This list contains over 300 e-mail header fields with their description and additional information.
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The header "ARC-Authentication-Results" is part of the Authenticated Received Chain (ARC) protocol. ARC is used to append message authentication information.
The header "ARC-Message-Signature" is part of the Authenticated Received Chain (ARC) protocol. ARC is used to append message authentication information.
The header "ARC-Seal" is part of the Authenticated Received Chain (ARC) protocol. ARC is used to append message authentication information.
abuse@domain.tldThe header field "Abuse-Reports-To" contains the address to which complaints about an e-mail received can be addressed.
(Non-standard)
de, enThe header field "Accept-Language" is the language desired by the sender for replies. It is also possible to specify several languages separated by a comma.
The header field "Also-Control" marks the article as being a control message in addition to being a normal news article and specifies the desired actions.
(Is obsolete, concerns Netnews/Usenet)
The header field "Alternate-Recipient" controls whether this message can be forwarded to another recipient, e.g. a postmaster, if delivery to the intended recipient is not possible.
The header field "Apparently-To" is inserted by Sendmail if there are no recipients ("To") in the original message that contain the recipients derived from the SMTP envelope.
<moderator@domain.tld>The header field "Approved" contains the mail addresses and possibly also the names of the moderators who approve the message before it is published. This header is mainly used in moderated news groups and group control messages.
(Concerns Netnews/Usenet)
yesThe header field "Archive" provides an indication of the poster's intent regarding preservation of the article in publicly accessible long-term or permanent storage.
(Concerns Netnews/Usenet)
<https://www.server.tld/archive/msg/12345>The header field "Archived-At" contains a URI in angle brackets that refers to the location of the archived message.
(Concerns Mail, concerns Netnews/Usenet)
The header field "Article-Names" contains a reference to specially important articles for a particular Usenet Newsgroup.
(Is obsolete, concerns Netnews/Usenet)
The header field "Article-Updates" is used to update an article.
(Is obsolete, concerns Netnews/Usenet)
domain.tld; spf=pass smtp.mailfrom=example.tldThe header field "Authentication-Results" contains the authentication results of a mail server.
previous.domain.tld; spf=pass smtp.mailfrom=example.tldThe header field "Authentication-Results-Original" contains the authentication results of a previous mail server. When a mail server authenticates a message, it writes the result to the header field "Authentication-Results". If this field already exists, its contents can be saved in the field "Authentication-Results-Original".
(Non-standard)
Auto-Submitted: auto-repliedThe header field "Auto-Submitted" indicates that the message originates from an automatic process or an automatic responder and not from a human. Possible values can be "no", "auto-generated" or "auto-replied", followed by further information.
The header field "Autoforwarded" indicates that this massage was automatically forwarded.
The header field "Autosubmitted" indicates that this massage was automatically submitted.
Webmaster <webmaster@domain.tld>The header field "Bcc" (Blind Carbon Copy) contains additional recipients who should receive the message as "invisible copy". Those additional recipients in the BCC field can not be seen by the other recipients. The recipients in the To and CC field are visible to all recipients.
The header field "Cancel-Key" is used to cancel posted messages later.
(Concerns Netnews/Usenet)
The header field "Cancel-Lock" is used to cancel posted messages later.
(Concerns Netnews/Usenet)
Name <name@domain.tld>The header field "Cc" (Carbon Copy) contains additional recipients who should receive the message in "Copy". This information is for administrative purposes only. However, the e-mail is delivered as if the addresses were contained in the To header.
Authenticated sender is <name@domain.tld>The header field "Comments" contains comments of the author or his mail program to the message.
(Concerns Mail, concerns Netnews/Usenet)
The header field "Content-Alias" is used in addition to "Content-Location" if this content part can be retrieved through more than one URI. Only one of them is allowed in the "Content-Location", the other can be specified in "Content-Alias".
(Non-standard)
The header field "Content-Language" can be attached to a MIME body part to indicate availability of some alternative form of the data it contains. For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
https://www.domain.tld/mailcontent/The header field "Content-Base" contains the absolute base URI for other header fields or HTML tags in this MIME body part that do not have a BASE attribute. For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
The header field "Content-Class" contains type information of the content in some class hierarchy. Class hierarchies are commonly used to classify data structures in software development. Also used by Microsoft products and may contain values such as "fax", "call", or "missedcall".
allowedThe header field "Content-Conversion" indicates whether the text of this message may be converted from one character set to another. Possible values are "prohibited" and "allowed". ("Content-Conversion" equals "Conversion", but is not a standard.)
(Non-standard)
The header field "Content-Description" contains a description of a particular MIME body part of a message. For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
attachment; filename="invoice.pdf"The header field "Content-Disposition" indicates whether a MIME body part is to be shown inline or is an attachment. The header field can also indicate a suggested filename for use when saving an attachment to a file. For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
25The header field "Content-Duration" contains the time duration of MIME body part content, in seconds (e.g., for audio or video). For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
The header field "Content-ID" specifies a unique identifier for one MIME body part of a message. For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
The header field "Content-Identifier" contains a text string that identifies the content of a message.
(Is obsolete)
de-AT, en-USThe header field "Content-Language" includes a code for the natural language used in a MIME body part, e.g. "en" for English. It is also possible to specify several languages separated by a comma. For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
12345The header field "Content-Length" is inserted by some mail programs to specify the size of the message text in bytes. Using this header field when sending a message can cause problems.
(Non-standard, Discouraged)
image/123The header field "Content-Location" specifies an URI that labels the content of a MIME body part in whose heading it is placed. For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message. Example: <img src="image/123"> displays the image from the body part with the header field "Content-Location: image/123".
The header field "Content-MD5" contains the checksum of the MIME body part content to ensure that it has not been modified. For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
The header field "Content-Return" indicates whether the content of a message is to be returned with non-delivery notifications.
(Is obsolete)
The header field "Content-SGML-Entity" contains information from the SGML entity declaration corresponding to the entity contained in the body of the body part.
(Non-standard)
quoted-printableThe header field "Content-Transfer-Encoding" specifies how the message text or the MIME body part text is encoded. Usual values are "quoted-printable", "base64", "7bit" and "8bit". For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
text/plain; charset=ISO-8859-1The header field "Content-Type" indicates the type of the message or MIME body part. For example, "text/plain" for text messages or "text/html" for HTML messages are common. "charset" is followed by the character set used. For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
(& (Type="image/tiff") (color=Binary) (image-file-structure=TIFF-S) (dpi=200) (dpi-xyratio=200/100) (paper-size=A4) (image-coding=MH) (MRC-mode=0) (ua-media=stationery) )The header field "Content-features" can be used to annotate a MIME body part with a media feature expression, to indicate features of the body part content. For example, a MIME body part can contain an attachment such as an image or document, or the text or HTML version of the message.
The header field "Control" marks the article as a control message and specifies the desired actions (in addition to the usual actions of storing and/or relaying the article).
(Concerns Netnews/Usenet)
allowedThe header field "Conversion" indicates whether the text of this message may be converted from one character set to another. Possible values are "prohibited" and "allowed".
The header field "Conversion-With-Loss" indicates that the body of this message may not be converted from one character set to another if information will be lost. Possible values are "prohibited" and "allowed".
OpenDKIM Filter v2.11.0 host.domain.tld ABCDEF1234The header field "DKIM-Filter" contains the product name and version of the DKIM filter, as well as the job ID. DomainKeys Identified Mail (DKIM) is an email authentication method designed to detect forged sender addresses in emails.
v=1; a=rsa-sha1; c=relaxed/relaxed; s=k1; d=xyz.tld; h= ...The header field "DKIM-Signature" contains the DKIM signature. DomainKeys Identified Mail (DKIM) is an email authentication method designed to detect forged sender addresses in emails.
The header field "DL-Expansion-History" contains a trace of distribution lists passed.
Wed, 6 Sept 2018 10:02:47 +0000The header field "Date" contains the creation time or the time of sending. This time is inserted by the sender's mail program. The time is specified in the local time of the sending computer. After the time follows either the deviation to the UTC (e.g. "+0200" for +2 hours), or in some cases also the time zone.
(Concerns Netnews/Usenet)
The header field "Date-Received" records the date and time that the article was first received on the local system. If this header field is present in an article being transmitted from one host to another, the receiving host should ignore it and replace it with the current date.
(Concerns Netnews/Usenet, is obsolete)
The header field "Deferred-Delivery" provides information about deferred delivery service to the recipient.
The header field "Delivered-To" is used by some automatic services (mainly MLMs and autoresponders) for the purpose of loop detection. The service adds this header to outgoing messages, with its e-mail address as a value, and discards incoming messages which already have it.
(Non-standard)
The header field "Delivery-Date" contains the time when a message was delivered to its recipient.
The header field "Discarded-X400-IPMS-Extensions" can be used in Internet mail to indicate X.400 IPM extensions that could not be mapped to Internet mail format.
The header field "Discarded-X400-MTS-Extensions" can be used in Internet mail to indicate X.400 MTS extensions that could not be mapped to Internet mail format.
The header field "Disclose-Recipients" indicates whether recipients are to be told the names of other recipients of the same message. This is primarily an X.400 facility. In X.400, this is an envelope attribute and refers to disclosure of the envelope recipient list. Disclosure of other recipients is done in Internet mail via the "To", "Cc" and "Bcc" header fields.
The header field "Disposition-Notification-Options" is used for optional modifiers on disposition notification requests.
name@domain.tldThe header field "Disposition-Notification-To" contains the mail address to which the read receipt for a message is to be sent.
deThe header field "Distribution" indicates geographical or organizational limits for the distribution of an article. Common values are "world", "local", "usenet", countries or country codes.
(Concerns Netnews/Usenet)
a=rsa-sha1; c=nofws; q=dns; s=k1; d=xyz.tld; b= ...The header field "DomainKey-Signature" contains the DomainKey signature. DomainKeys (DK) is an deprecated email authentication method designed to detect forged sender domains in emails.
good (test mode)The header field "DomainKey-Status" contains the results for domain-based e-mail authentication.
The header field "Downgraded-Bcc" contains the original header field ("Bcc") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Cc" contains the original header field ("Cc") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Disposition-Notification-To" contains the original header field ("Disposition-Notification-To") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Final-Recipient" contains the original header field ("Final-Recipient") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-From" contains the original header field ("From") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-In-Reply-To" contains the original header field ("In-Reply-To") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Mail-From" contains the original information from the SMTP envelope ("MAIL FROM") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Message-Id" contains the original header field ("Message-Id") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Original-Recipient" contains the original header field ("Original-Recipient") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Rcpt-To"" contains the original information from the SMTP envelope ("RCPT TO") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-References" contains the original header field ("References") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Reply-To" contains the original header field ("Reply-To") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Resent-Bcc" contains the original header field ("Resent-Bcc") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Resent-Cc" contains the original header field ("Resent-Cc") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Resent-From" contains the original header field ("Resent-From") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Resent-Message-Id" contains the original header field ("Resent-Message-Id") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Resent-Reply-To" contains the original header field ("Resent-Reply-To") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Resent-Sender" contains the original header field ("Resent-Sender") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Resent-To" contains the original header field ("Resent-To") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Return-Path" contains the original header field ("Return-Path") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-Sender" contains the original header field ("Sender") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "Downgraded-To" contains the original header field ("To") if the extension "Email Address Internationalization" (UTF8SMTP) is used, which allows UTF-8 characters in the message header. To allow mail servers that do not support this extension to process the message, the headers must be encoded.
The header field "EDIINT-Features" indicates the originating user agent is capable of supporting the EDIINT features listed. EDIINT stands for Electronic Data Interchange - Internet Integration.
Eesst-Version: 1.0The header field "Eesst-Version" contains the version of the EESST exchange format to which the displayed school transcript conforms. EESST stands for Email Exchange of Secondary School Transcripts.
The header field "Encoding" is used in several different ways by different mail systems. Some use it for a kind of content-type information, some for encoding and length information, some for a kind of boundary information, and some in other ways.
The header field "Encrypted" contains message encryption information.
(Is obsolete)
The header field "Envelope-To" contains the recipients from the SMTP envelope ("RCPT TO") if they are not included in the "To" or "Cc" header fields.
(Non-standard)
Errors-To: mail@domain.tldThe header field "Errors-To" contains the mail address to which delivery errors are to be sent, such as for a non-existent recipient.
(Non-standard)
The header field "Expires" indicates a date and time when the poster deems the article to be no longer relevant and could usefully be removed.
(Concerns Mail, concerns Netnews/Usenet)
The header field "Expiry-Date" contains the time at which a message loses its validity. This header field has changed to "Expires".
The header field "Fax" contains the fax number of the originator.
(Non-standard)
The header field "Fcc" contains the name of file in which a copy of this message is stored.
(Non-standard)
ABC:12345:xyz123:senderidThe header field "Feedback-ID" is used by Google and contains information about bulk emails. Bulk email senders can use Feedback Loop (FBL) to identify campaigns that result in high complaint rates among Gmail users. Feedback Loop is especially useful for email service providers to prevent abuse of their services. The FBL data always refers only to recipients with the address "@gmail.com". The content consists of 4 parts separated by a colon. All parts (including the sender ID) are chosen by the sender, but Google recommends the format: Campaign ID:Customer ID:Email type:Sender ID.
(Non-standard)
The header field "Followup-To" indicates in which newsgroups the poster requested the follow-up. "Followup-To" should only be included if the content differs from "Newsgroups".
(Concerns Netnews/Usenet)
controlling@domain.tldThe header field "For-Approval" contains the primary recipients, who are requested to approve the information in this message or its attachments.
(Non-standard)
manager@domain.tldThe header field "For-Comment" contains the primary recipients, who are requested to comment on the information in this message or its attachments.
(Non-standard)
administrator@domain.tldThe header field "For-Handling" contains the primary recipients, who are requested to handle the information in this message or its attachments.
(Non-standard)
v=1 ; ip4=10.1.2.3The header field "Form-Sub" indicates that the message was sent in response to the submission of a web form. The tags "ip4" or "ip6" contain the IP address from where the web form was sent. Parts of the IP address can be anonymized with "x". If no address can be determined, "ip=none" is inserted.
Name <name@domain.tld>The header field "From" contains the mail address and possibly also the name of the sender. This information is inserted by the mail program of the sender.
(Concerns Mail, concerns Netnews/Usenet)
The header field "Generate-Delivery-Report" indicates whether a delivery report is wanted at successful delivery. Default is not to generate such a report.
HighThe header field "Importance" indicates the importance of the message. The value has no influence on the speed of transmission. This header is used in spam with a high priority value.
webmaster@domain.tldThe header field "In-Reply-To" contains in case of an answer, the message ID of the answered message for a reply.
The header field "Incomplete-Copy" indicates that body parts are missing.
Injection-Date: Sun, 6 Oct 2019 08:04:46 UTCThe header field "Injection-Date" contains the date and time when the article was sent to the network. With this time, news servers can search for outdated articles.
(Concerns Netnews/Usenet)
The header field "Injection Info" contains information from the sending news server about how an article got into the Netnews system. This helps track the true origin of the article. It can also provide one or more addresses to which complaints can be made about the article's poster.
(Concerns Netnews/Usenet)
=?us-ascii?q? Hdhd83K ... hd34Dk3 ?=The header field "IronPort-PHdr" is inserted by the Graymail engine of Cisco Email Security appliances and contains encoded proprietary information. The data contains information for debugging problems with Graymail configuration and, according to Cisco, cannot be decoded by the customer.
(Non-standard)
7jfwH3JKs ... fj4L3==The header field "IronPort-SDR" is inserted by Cisco Email Security appliances and contains encoded information.
(Non-standard)
jabberuser@domain.tldThe header field "Jabber ID" contains the XMPP address of the sender. Special characters in the address are encoded.
(Concerns Mail, concerns Netnews/Usenet)
Keyword1, Keyword2The header field "Keywords" contains a comma-separated list of important words and phrases that might be useful for the recipient.
(Concerns Mail, concerns Netnews/Usenet)
enThe header field "Language" includes a code for the natural language used in a message, e.g. "en" for English.
The header field "Latest-Delivery-Time" contains the latest desired delivery time, but will not be acted on by the SMTP infrastructure
23The header field "Lines" contains the number of line breaks (CRLF) in the message body. "Lines" is deprecated and should be ignored and no longer generated by programs.
(Is obsolete)
<https://www.domain.tld/list/archive/> (Web Archive)The header field "List-Archive" contains the URL to be used to browse the mailing list archive.
The header field "List-Digest" contains the URL to use to get a subscription to the digest version of the mailing list from which this message was relayed.
(Non-standard)
<mailto:newsletter@domain.tld?subject=help> (Help)The header field "List-Help" contains the URL to use to get information about the mailing list from which this message was relayed.
"Example Mailing List" <list-example.domain.tld>The header field "List-ID" stores an identification of the mailing list through which this message was distributed.
<mailto:webmaster@domain.tld> (Contact for Help)The header field "List-Owner" identifies the path to contact a human administrator for the list. The URL may contain the address of a administrator for the list, the mail system administrator, or any other person who can handle user contact for the list. There is no need to specify "List-Owner" if it is the same person as the mail system administrator (postmaster).
<mailto:newsletter@domain.tld>The header field "List-Post" describes the method for posting to the list. This is typically the address of the list, but may be a moderator, or potentially some other form of submission. For the special case of a list that does not allow posting (e.g., an announcements list), the List-Post field may contain the special value "NO".
The header field "List-Software" contains information about the software used in a mailing list expander through which this message has passed.
(Non-standard)
<http://lists.domain.tld/newsletter>, <mailto:newsletter-request@domain.tld?subject=subscribe>The header field "List-Unsubscribe" describes the command (preferably using mail) to directly subscribe the user (request addition to the list).
<http://lists.domain.tld/newsletter>, <mailto:newsletter-request@domain.tld?subject=unsubscribe>The header field "List-Unsubscribe" describes the command (preferably using mail) to directly unsubscribe the user (removing them from the list).
List-Unsubscribe=One-ClickThe header field "List-Unsubscribe-Post" indicates whether an one-click unsubscription from the mailing list is available. A mail receiver can do a one-click unsubscription by performing an HTTPS POST to the HTTPS URI in the "List-Unsubscribe" header field. It sends the key/value pair in the "List-Unsubscribe-Post" header field as the request body.
MIME-Version: 1.0The header field "MIME-Version" contains the version of the Multipurpose Internet Mail Extensions (MIME). The MIME are specifications that concern special characters and multimedia and are used for compatibility when exchanging messages.
The header field "MMHS-Acp127-Message-Identifier" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Authorizing-Users" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Codress-Message-Indicator" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Copy-Precedence" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Exempted-Address" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Extended-Authorisation-Info" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Handling-Instructions" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Message-Instructions" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Message-Type" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Originator-PLAD" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Originator-Reference" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Other-Recipients-Indicator-CC" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Other-Recipients-Indicator-To" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Primary-Precedence" is used for message transmission with the Military Message Handling System (MMHS).
The header field "MMHS-Subject-Indicator-Codes" is used for message transmission with the Military Message Handling System (MMHS).
4 (ultra)The header field "MT-Priority" conveys the priority of the message transfer when a message is forwarded via mail servers that do not support the SMTP extension MT-PRIORITY.
The header "Mail-Copies-To" is used in Netnews articles to indicate that followup (=replies) should be sent to the indicated e-mail address.
(Concerns Netnews/Usenet, non-standard)
The header field "Mail-Followup-To" contains the addresses that a mail program should use for the "Follow-up" function. Otherwise "Reply-To", "To" and "Cc" are normally used.
(Concerns Netnews/Usenet, non-standard)
bounce@domain.tldThe header "Mail-Reply-Requested-By" contains the address to which notifications are to be sent and a request to get delivery notifications.
(Non-standard)
The header field "Mail-Reply-To" contains the mail address of the author to whom the reply should be sent. A mail program with the function "Reply to author" should use this address.
(Concerns Netnews/Usenet, non-standard)
The header file "Mail-System-Version" contains information about the software used to send the message.. Usual information is the name and version number of the software, but also the URL or other information is possible.
(Non-standard)
The header file "Mailer" contains information about the software used to send the message. Usual information is the name and version number of the software, but also the URL or other information is possible.
(Non-standard)
Message-Context: text-messageThe header field "Message-Context" provides information about the context and presentation characteristics of a message. Can have the values "voice-message", "fax-message", "pager-message", "multimedia-message", "text-message" or "none".
Message-ID: <DCEA2913.6003005@domain.tld>The header field "Message-ID" contains the unique identification of the message. This identifier is generated by the mail program, often from the date. If the Message-ID field is missing, it is usually created and inserted by a mail server.
(Concerns Mail, concerns Netnews/Usenet)
The header field "Message-Type" is only used with the value "Delivery Report" to indicate that this is a delivery report gatewayed from X.400.
Sun, 6 Oct 2019 08:04:46 UTCThe header field "NNTP-Posting-Date" contains the date and time when the article was sent to the network. With this time, news servers can search for outdated articles. This header field was replaced by "Injection-Date".
(Concerns Netnews/Usenet, is obsolete)
10.1.2.3The header field "NNTP-Posting-Host" is added to the header of a posted article by the server. The contents of the header is either the IP address or the fully qualified domain name of the client host posting the article. This header field was replaced by "Injection-Info".
(Concerns Netnews/Usenet, is obsolete)
alt.binariesThe header field "Newsgroups" contains a list of Usenet newsgroups in which the article was posted. Multiple newsgroups are separated by a comma.
(Concerns Netnews/Usenet)
recipient@domain.tldThe header field "Notice-Requested-Upon-Delivery-To" requests a confirmation when the delivery has been made to the specified recipients.
<OLDMSG.35557262@domain.tld>The header field "Obsoletes" contains the reference to a previous message being corrected and replaced. "Obsoletes" was renamed to "Supersedes".
(Is obsolete)
Example Company Ltd.The header field "Organisation" specifies the organization or company name of the sender. The organization can be set in the mail program.
(Non-standard)
Example Company Ltd.The header field "Organization" specifies the organization or company name of the sender. The organization can be set in the mail program.
(Concerns Mail, concerns Netnews/Usenet)
The header field "Original-Encoded-Information-Types" indicates which body part types occur in this message.
"Sender Name" <name@domain.tld>The header field "Original-From" contains the original sender ("From") if it is changed by a Sieve script. Sieve is used for simple filtering of mails.
<CFBD8411.8853008@domain.tld>The header field "Original-Message-ID" contains the original message identifier when the message is resent with alternative content format.
webmaster@domain.tldThe header field "Original-Recipient" contains the original recipient of the message. The mail server may be able to extract this from the SMTP command RCPT TO. This is used to record the original recipient if the recipient address is changed by a mail server during delivery.
sender@domain.tldThe header field "Original-Sender" holds the content of a "Sender" header field in an original message received by an incoming gateway, preserving it while the incoming gateway adds its own Sender header field.
(Concerns Netnews/Usenet)
Original example subjectThe header field "Original-Subject" contains the original sender ("Subject") if it is changed by a Sieve script. Sieve is used for simple filtering of mails.
The header file "Originating-Client" contains information about the software used to send the message. Usual information is the name and version number of the software, but also the URL or other information is possible.
(Non-standard)
The header field "Originator" is sometimes used in Usenet News in similar ways to "Sender". (The header field "Sender" contains the technical sender, if different from the sender in the "From" field, such as mailing lists.)
(Concerns Netnews/Usenet, non-standard)
The header field "Originator-Info" contains information about the authentication of the originator in a format which is not easily used to send email to.
(Concerns Mail, concerns Netnews/Usenet)
return@domain.tldThe header field "Originator-Return-Address" contains the return address of the originator.
The header field "PICS-Label" contains the ratings label to control selection (filtering) of messages according to the PICS protocol. PICS stands for Platform for Internet Content Selection.
nntp.server3.tld!news.server2.tld!news.server1.tld!not-for-mailThe header field "Path" indicates the route that an article has taken since its injected into the Usenet. Each server that processes an article is required to prepend at least one entry. This is primarily to ensure that news servers are able to avoid sending an article to already known sites, especially to the sender.
(Concerns Netnews/Usenet)
The header field "Phone" contains the phone number of the originator.
(Non-standard)
alt.binariesThe header field "Posted-To" contains the names of newsgroups to which this message was sent. When a message is sent to both Netnews and email, this header is used in the email version of the message to indicate to which newsgroup it was sent. This header therefore contains the same information as "Newsgroups" in the Netnews version of the message.
(Non-standard)
The header field "Posting-Version" identifies the software responsible for entering this message into the network.
(Concerns Netnews/Usenet, is obsolete)
bulkThe header field "Precedence" is used to indicate the priority that can affect the speed and performance of message transmission. Common values are "bulk" and "first-class". Also used to control automatic replies and stop mailing list loops.
The header field "Prevent-NonDelivery-Report" indicates whether a non-delivery report is wanted on delivery error. Default is to generate such a report.
urgentThe header field "Priority" indicates the priority of the message. The value can influence the speed of the message transmission. Possible values are "normal", "urgent" and "non-urgent". Spam messages often use "urgent".
[X]The header field "Privicon" contains ASCII characters that indicate how a message should be handled, such as "Do not print" or "Share".
sender@domain.tldThe header "Read-Receipt-To" requests an automated confirmation notice when the message is received or read. This header field is ignored by most mail programs.
(Non-standard)
from sender.tld (sender.tld [10.1.2.3]) by server.tld with SMTP; 4 Oct 2019 15:40:53 +0200The header field "Received" contains information about the sender, the receiver and the received time of a message. This header is added by the receiving mail server as the top line. Depending on the number of mail servers involved, several "Received" header fields may be included.
pass (example.tld: domain of name@domain.tld designates 10.1.2.3 as permitted sender)The header field "Received-SPF" contains information about the verification of a sender domain via Sender Policy Framework (SPF).
<DCEA2913.6003005@domain.tld>The header field "References" contains the message IDs of related messages. In the case of a reply, this would be the message ID of the answered message. This header field is used by mail programs to sort the messages or to display them hierarchically.
(Concerns Mail, concerns Netnews/Usenet)
bounce@domain.tldThe header "Registered-Mail-Reply-Requested-By" contains the address to which notifications are to be sent and a request to get delivery notifications.
(Non-standard)
The header field "Relay-Version" shows the version of the program responsible for the transmission of this article over the immediate link, that is, the program that is relaying the article from the next site.
(Concerns Netnews/Usenet, is obsolete)
<OLDMSG.35557262@domain.tld>The header field "Replaces" contains the reference to a previous message being corrected and replaced. "Replaces" has the same functionality as "Supersedes".
The header field "Reply-By" contains the latest time by which a reply is requested (not demanded).
mail@domain.tldThe header field "Reply-To" may contain an alternative response address if the response is not to be sent to the From address.
(Concerns Mail, concerns Netnews/Usenet)
The header field "Reply-To2" is used by some mail systems to indicate a better form of the e-mail address of the sender. Some mailing list expanders puts the name of the list in this header field.
(Non-standard)
The header field "Require-Recipient-Valid-Since" contains the time when the sender knew the owner of the recipient's mailbox. This can be used to detect changes in mailbox ownership and prevent emails from being delivered to the wrong recipient.
bcc-recipient@domain.tldThe header field "Resent-To" contains the mail addresses of the Bcc-recipients to whom the message was resent.
cc-recipient@domain.tldThe header field "Resent-To" contains the mail addresses of the Cc-recipients to whom the message was resent.
Wed, 6 Sept 2018 19:46:29 +0000The header field "Resent-Date" contains the date and time that a message is reintroduced by a user into the message transfer system (forwarded).
from@domain.tldThe header field "Resent-From" contains the address of the person who reintroduced the message into the message transfer system or in whose name the message was resent.
<DCEA2914.9484449@domain.tld>The header "Resent-Message-ID" contains the identification of the resent message.
reply-to@domain.tldThe header field "Resent-Reply-To" can contain an alternative reply address for the resent message if the reply is not to be sent to the address entered in "Resent-From".
(Is obsolete)
sender@domain.tldThe header field "Resent-Sender" contains the mail address of the person who has reintroduced the message into the message transfer system, if this differs from "Resent-From".
recipient@domain.tldThe header field "Resent-To" contains the mail addresses of the recipients to whom the message was resent.
name@domain.tldThe "Return-Path" header contains the return address if delivery of the message was not possible. An error message is added to the original email from the mail server that failed to deliver the message. The return path can also be added by a mail server based on the specification under "MAIL FROM".
bounce@domain.tldThe header field "Return-Receipt-Requested" contains an address to which delivery notifications are to be sent.
(Non-standard)
name@domain.tldThe header "Return-Receipt-To" contains the mail-address to which the delivery confirmation is to be sent by the mail server.
(Non-standard)
SIO-Label: marking="EXAMPLE CONFIDENTIAL"; fgcolor=black; bgcolor=red; type=":x411"; label="MQYGASkCAQM="The header field "SIO-Label" contains information about SIO labels as key/value pairs. A mail client that generates a message can, if configured, offer the user a menu with sensitivities for selection and, when selecting, insert the display markings, foreground and background colors as well as security label parameters associated with this selection into the "SIO-Label" header field of the message.
SIO-Label-History: marking="EXAMPLE CONFIDENTIAL"; fgcolor=black; bgcolor=red; type=":xml"; label*0=" ... "; change=delete; changed-by="delete.example.com"; changed-at="18 Feb 2019 9:24 PDT"; changed-comment="delete"The header field "SIO-Label-History" contains information on the change history of SIO labels. A mail client that generates a message can, if configured, offer the user a menu with sensitivities for selection and, when selecting, insert the display markings, foreground and background colors as well as security label parameters associated with this selection into the "SIO-Label" header field of the message.
The header field "See-Also" contains references to other related articles in Netnews.
(Concerns Netnews/Usenet, is obsolete)
name@domain.tldThe header field "Sender" contains the technical sender, if different from the sender in the "From" field, such as mailing lists.
(Concerns Mail, concerns Netnews/Usenet)
NormalThe header field "Sensitivity" indicates how sensitive it is to forward this message to people other than the specified recipients. Common values are "Personal", "Private", "Company-Confidential", "Internal" and "Normal".
Solicitation: net.example:ADV,org.example:ADV:ADLTThe header field "Solicitation" contains one or more solicitation class keywords.
The header field "Speech-Act" contains the speech act categorization of a message, examples of speech acts are Question, Idea, More, Promise, Sad, Happy, Angry, Summary, Decision.
(Non-standard)
The header field "Status" is used by some mail delivery systems to indicate the status of delivery for this message when stored. Common values of this field are: U - message is not downloaded and not deleted, R - message is read or downloaded, O - message is old but not deleted, D - to be deleted, N - new, or a combination of these values.
(Non-standard)
Example subjectThe header field "Subject" contains the subject of the message.
(Concerns Mail, concerns Netnews/Usenet)
Some examplesThe header field "Summary" contains a short phrase summarizing the article's content.
(Concerns Netnews/Usenet)
<OLDMSG.35557262@domain.tld>The header field "Supersedes" contains the reference to a previous message being corrected and replaced.
(Concerns Mail, concerns Netnews/Usenet)
receiver-domain.tldThe header field "TLS-Report-Domain" contains information about the SMTP TLS Reporting.
sender-domain.tldThe header field "TLS-Report-Submitter" contains information about the SMTP TLS Reporting.
NoThe header field "TLS-Required" is used for messages for which the originator requests that recipient TLS policy be ignored. This might be done, for example, to report a misconfigured mail server, such as an expired TLS certificate.
The header field "Telefax" contains the fax number of the originator.
(Non-standard)
AdxySx3+9sgCxf34RIasS7KZ/0zH3Q==The header field "Thread-Index" is used by Microsoft applications and indicates the relative position of this message within a conversation thread, similar to "References" and "In-reply-To". Mail servers or mail clients from Microsoft (such as Exchange or Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
Example subjectThe header field "Thread-Topic" is used by Microsoft applications and contains the original subject, without any prefixes like "Re:" or "Fwd:". Mail servers or mail clients from Microsoft (such as Exchange or Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
"Webmaster" <webmaster@domain.tld>, name@domain.tld, support@domain.tld (Support Center)The header field "To" contains one or more recipients. Multiple addresses must be separated by a comma. The order of addresses and names may vary.
The header field "Translated-By" contains the mailbox of the person who made the translation.
(Non-standard)
The header field "Translation-Of" contains a reference to the Message-ID of a message, which the current message is a translation of.
(Non-standard)
ExampleNewsReader 1.0The header field "User-Agent" contains the name and usually also the version number of the program used for sending the message.
(Concerns Netnews/Usenet)
md=somebank.example; mc=transaction; mv=certifier-a.example:certifier-b.example;The header field "VBR-Info" contains information about the "Vouch By Reference" (VBR) protocol used to add third-party certifications to mails.
Header fields beginning with "X-" are usually not standardized. They are used by applications such as spam filters, anti-virus software, mail servers, and mail clients to add information to a message.
(Non-standard)
de, enThe header field "X-Accept-Language" indicates the languages accepted by the sender. Answers to this message should be written in one of these languages.
(Non-standard)
account1The header field "X-Account-Key" is added by Mozilla Thunderbird to indicate the internal name of the account with which the message was received.
(Non-standard)
admin@domain.tldThe header field "X-Admin" contains the e-mail address of administrator of a server, through which this message was submitted.
(Non-standard)
FalseThe header field "X-Amp-File-Uploaded" is inserted by Cisco Email Security Appliances and contains information from the Advanced Malware feature.
(Non-standard)
FILE UNKNOWNThe header field "X-Amp-Original-Verdict" is inserted by Cisco Email Security Appliances and contains information from the Advanced Malware feature. Possible values are "File unknown" and "Verdict unknown".
(Non-standard)
CleanThe header field "X-Amp-Result" is inserted by Cisco Email Security Appliances and contains the result of malware detection.
(Non-standard)
Sender Address Domain - domain.tldThe header field "X-AntiAbuse" contains information for tracking abuse (spam, phishing, fraud, etc.).
(Non-standard)
AV-Software 1.2.3 (VirDef: 18.10.2019), Outbound messageThe header field "X-Antivirus" usually contains the name and the version number of the anti-virus software, as well as possibly further information, such as the date of the virus definitions.
(Non-standard)
X-Antivirus-Status: CleanThe header field "X-Antivirus-Status" is used to note the result of a virus scan.
(Non-standard)
The header field "X-Apparently-To" is an alternative to "Apparently-To", which is inserted by Sendmail if there are no recipients ("To") in the original message that contain the recipients derived from the SMTP envelope.
(Non-standard)
<https://www.server.tld/archive/msg/12345>The header field "X-Archived-At" contains a URI in angle brackets that refers to the location of the archived message. This header is a precursor of "Archived-At" and should no longer be used.
(Concerns Mail, concerns Netnews/Usenet)
The header field "X-AttachmentOrder" is used by Microsoft mail clients and contains a list of file names for the audio file attachments that are to be played as part of a message. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
AllThe header field "X-Auto-Response-Suppress" is used by Microsoft mail clients and specifies whether a client or server application will forego sending automated replies in response to this message. The value can be "None" or "All". Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
The header field "X-CallID" is used by Microsoft mail clients and contains a unique identifier associated with the phone call. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
The header field "X-CallingTelephoneNumber" is used by Microsoft mail clients and contains the telephone number of the caller associated with a voice mail message. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
abuse@domain.tldThe header field "X-Complaints-To" contains the address to which complaints about an e-mail received can be addressed.
(Non-standard)
sender@domain.tldThe header "X-Confirm-Reading-To" requests an automated confirmation notice when the message is received or read. This header field is ignored by most mail programs.
(Non-standard)
Header fields beginning with "X-CrossPremisesHeaders" are typically inserted by Microsoft Exchange when a message is sent from the on-premises environment to Exchange Online.
(Non-standard)
host.domain.tldThe header field "X-CrossPremisesHeadersFilteredBySendConnector" is used by Microsoft Exchange. For a message sent from the on-premises environment to Exchange Online, this header field contains the Edge Transport Server on which the cross-premises headers were filtered.
(Non-standard)
bulkThe header field "X-Distribution" with the value "bulk" is used by Pegasus Mail when sending a message with many recipients. This is intended to detect and filter spam messages sent with Pegasus Mail.
(Non-standard)
42df9e9f-e7f6-20af-b827-e4651f674820The header "X-EOPTenantAttributedMessage" is used by Microsoft Office 365 and contains a GUID which represents a unique Office 365 tenant.
(Non-standard)
noname@example.tldThe header field "X-Env-From" is used by some mail servers to enter the address given in the SMTP dialog ("MAIL FROM").
(Non-standard)
noname@example.tldThe header field "X-Env-Sender" is used by some mail servers to enter the address given in the SMTP dialog ("MAIL FROM").
(Non-standard)
name@domain.tldThe header field "X-Envelope-From" contains the sender from the SMTP envelope ("MAIL FROM") if it is not the same as the senders in the "From" or "Sender" header fields.
(Non-standard)
noname@example.tldThe header field "X-Envelope-Sender" is used by some mail servers to enter the address given in the SMTP dialog ("MAIL FROM").
(Non-standard)
webmaster@domain.tldThe header field "X-Envelope-To" contains the recipients from the SMTP envelope ("RCPT TO") if they are not included in the "To" or "Cc" header fields.
(Non-standard)
name@domain.tldThe header field "Errors-To" contains the mail address to which delivery errors are to be sent, such as for a non-existent recipient.
(Non-standard)
The header field "X-Face" contains a 48x48 bitmap picture of the sender of this message.
(Non-standard)
The header field "X-FaxNumberOfPages" is used by Microsoft mail clients and contains the number of pages in a Fax object. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
Header fields beginning with "X-Forefront-" are inserted by a Microsoft Forefront application (spam filter and anti-virus software).
(Non-standard)
CIP:10.1.2.3;SFV:SKI;SFS:;DIR:INB;SFP:;SCL:-1;SRVR:PR3PR01MB8636;H:PR3PR08MB8377.eurprd02.prod.outlook.com;FPR:;SPF:None;LANG:de;The header "X-Forefront-Antispam-Report" is used by Microsoft Office 365 and contains information about spam protection. This information may include, but is not limited to, the IP connection address ("CIP:"), the spam rating ("SCL:"), the phishing rating ("PCL:") or the language used in the message ("LANG").
(Non-standard)
-2 (not scanned, spam filter disabled)The header field "X-GMX-Antispam" is inserted by GMX mail servers and contains information about the spam protection of GMX.
(Non-standard)
-1 (not scanned, may not use virus scanner)The header field "X-GMX-Antivirus" is inserted by GMX mail servers and contains information about the virus protection of GMX.
(Non-standard)
1The header field "X-GMX-HTML" is inserted by GMX mail servers.
(Non-standard)
f9Htf ... 1N12+The header field "X-GMX-UID" is inserted by GMX mail servers.
(Non-standard)
v=1; a=rsa-sha256; c=relaxed/relaxed; d=domain.tld; s=20191025; h=x-gm-message-state:message-id:date:subject:from:to:mime-version:content-transfer-encoding; bh=joset8yp ... HxQ==The header field "X-Google-DKIM-Signature" contains the DKIM signature of messages, sent via Google mail servers (e.g. GMail). DomainKeys Identified Mail (DKIM) is an email authentication method designed to detect forged sender addresses in emails.
(Non-standard)
delayed 555 seconds by postgrey-1.34 at servername; Fri, 04 Oct 2019 12:51:48 CESTThe header field "X-Greylist" contains information about the greylisting of a message. This is a method of fighting spam in which the message is not accepted by an unknown sender until a new delivery attempt is made.
(Non-standard)
The header field "X-IMAP" contains the UID, as defined in the IMAP standard. Only used in internal mailbox storage in some mail systems, should never be visible to a user.
(Non-standard)
Header fields beginning with "X-IronPort-" are inserted by Cisco Email Security appliances.
(Non-standard)
The header field "X-IronPort-Outbreak-Description" is inserted by Cisco Email Security Appliances and contains information from the Virus Outbreak Filtering feature.
(Non-standard)
The header field "X-IronPort-Outbreak-Status" is inserted by Cisco Email Security Appliances and contains information from the Virus Outbreak Filtering feature.
(Non-standard)
E=Sophos;i="5.11,510,1737454500"; d="scan'201,229";a="854730900"The header field "X-Ironport-AV" is inserted by Cisco Email Security Appliances and contains the encoded details pertaining to anti-virus scanning.
(Non-standard)
TrueThe header field "X-Ironport-Anti-Spam-Filtered" is inserted by Cisco Email Security Appliances and contains the indication (True or False) whether a message has been filtered for spam.
(Non-standard)
A7Bf948 ... 16A23BEQAThe header field "X-Ironport-Anti-Spam-Result" is inserted by Cisco Email Security Appliances and contains the hashed result of the spam filtering.
The header field "X-KLMS-AntiPhishing" is inserted by Kaspersky Security for Linux Mail Server into messages processed by the Anti-Phishing module.
(Non-standard)
The header field "X-KLMS-AntiSpam-Auth" is added by Kaspersky Security for Linux Mail Server and contains information about the authenticity of the message sender.
(Non-standard)
name@domain.tldThe header field "X-KLMS-AntiSpam-Envelope-From" is added by Kaspersky Security for Linux Mail Server and contains the message sender.
(Non-standard)
{FROM: no valid address in FROM, no dot}, {DNS response errors}The header field "X-KLMS-AntiSpam-Info" is added by Kaspersky Security for Linux Mail Server and contains the criteria used by the Anti-Spam module to assign the status to the message.
(Non-standard)
scan successfulThe header field "X-KLMS-AntiSpam-Interceptor-Info" is added by Kaspersky Security for Linux Mail Server and contains the result of the message scan. Possible values are: "protection disabled" if the Anti-Spam module is disabled. "timeout expired" if the message was queued for scanning, but has not been scanned due to timeout exceeded. "size exceeded" if the message was not queued for scanning due to its large size. "scan successfull" if the message successfully scanned und "fallback" if the message was queued for scanning, but has not been scanned due to an error.
(Non-standard)
35793 [Aug 20 2012]The header field "X-KLMS-AntiSpam-Lua-Profiles" is added by Kaspersky Security for Linux Mail Server.
(Non-standard)
noneThe header field "X-KLMS-AntiSpam-Method" is added by Kaspersky Security for Linux Mail Server and contains the successfully used spam recognition method.
(Non-standard)
1971238, 1971643, 1971629The header field "X-KLMS-AntiSpam-Moebius-Timestamps" is added by Kaspersky Security for Linux Mail Server.
(Non-standard)
20The header field "X-KLMS-AntiSpam-Rate" is added by Kaspersky Security for Linux Mail Server and contains the rating assigned to the message by the Anti-Spam module.
(Non-standard)
passThe header field "X-KLMS-AntiSpam-Spf" is added by Kaspersky Security for Linux Mail Server and contains information about checking a sender domain using Sender Policy Framework (SPF).
(Non-standard)
5.2.1The header field "X-KLMS-AntiSpam-Version" is added by Kaspersky Security for Linux Mail Server and contains the Anti-Spam module version.
(Non-standard)
Kaspersky Linux Mail Security 8.0.0.359, bases: 2012/08/20 04:12:00 #7814976The header field "X-KLMS-Antivirus" is added by Kaspersky Security for Linux Mail Server and contains info about the application (version, release date and number of antivirus signatures).
(Non-standard)
Clean, skippedThe header field "X-KLMS-AntiSpam-Status" is added by Kaspersky Security for Linux Mail Server and contains the status assigned to the message by the Anti-Spam module after scanning.
(Non-standard)
skipped, ContentFilteringThe header field "X-KLMS-Message-Action" is added by Kaspersky Security for Linux Mail Server and contains the action applied by the application to the message, and modules used in its scanning.
(Non-standard)
4The header field "X-KLMS-Rule-ID" is added by Kaspersky Security for Linux Mail Server and contains a list of IDs of the rules used in scanning the message.
(Non-standard)
The header field "X-List-Host" contains information about the software used in a mailing list expander through which this message has passed.
(Non-standard)
The header field "X-Listserver" contains information about the software used in a mailing list expander through which this message has passed.
(Non-standard)
The header field "X-Loop" is used by some automatic services (mainly MLMs and autoresponders) for the purpose of loop detection. The service adds this header to outgoing messages, with its e-mail address as a value, and discards incoming messages which already have it.
(Non-standard)
The header field "X-MIME-Autoconverted" contains information about conversion of this message on the path from sender to recipient, like conversion between MIME encoding formats. Note: Auto-conversion may invalidate digital seals and signatures.
(Non-standard)
Header fields beginning with "X-MS-" are usually inserted by a Microsoft application.
(Non-standard)
Header fields beginning with "X-MS-Exchange-" are usually inserted by a Microsoft Exchange Server or Exchange Online (Office 365).
(Non-standard)
InternetThe header "X-MS-Exchange-CrossTenant-FromEntityHeader" is used by Microsoft Office 365.
(Non-standard)
42df9e9f-e7f6-20af-b827-e4651f674820The header "X-MS-Exchange-CrossTenant-Id" is used by Microsoft Office 365 and often represents the GUID of the tenant which sent the message, but won't always, depending on how the mail routed through Exchange Online and if there were hops to third party devices as a message moved from one tenant to another.
(Non-standard)
HOSTEDThe header "X-MS-Exchange-CrossTenant-MailboxType" is used by Microsoft Office 365.
(Non-standard)
77f3c78b-32f0-40a9-4a52-02d94620b777The header "X-MS-Exchange-CrossTenant-Network-Message-Id" is used by Microsoft Office 365.
(Non-standard)
16 Oct 2019 19:43:25.8461 (UTC)The header "X-MS-Exchange-CrossTenant-OriginalArrivalTime" is used by Microsoft Office 365 and probably contains the original arrival time of the message.
(Non-standard)
TenantId=42df9e9f-e7f6-20af-b827-e4651f674820;Ip=[10.1.2.3];Helo=[host.name.domain.tld]The header "X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp" is used by Microsoft Office 365.
(Non-standard)
AV-Software;1;0;infoThe header "X-MS-Exchange-Organization-AVStamp-Mailbox" is used by Microsoft Office 365 and usually contains the name of the anti-virus software used, as well as any other information.
(Non-standard)
AnonymousThe header "X-MS-Exchange-Organization-AuthAs" is used by Microsoft Office 365.
(Non-standard)
ME7AUS01FT080.eop-AUS07.prod.protection.outlook.comThe header "X-MS-Exchange-Organization-AuthSource" is used by Microsoft Office 365.
(Non-standard)
trueThe header field "X-MS-Exchange-Organization-AutoForwarded" is used by Microsoft mail clients and indicates that this message has been automatically generated or automatically forwarded. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
2The header field "X-MS-Exchange-Organization-SCL" is used by Microsoft Exchange Server and specifies the phishing probability of the message. A value from 1 to 3 is probably not phishing, a value from 4 to 8 is probably phishing.
(Non-standard)
The header field "X-MS-Exchange-Organization-PRD" is used by Microsoft Exchange Server and contains the domain name of the last sender responsible for transmitting the current message. PRD stands for Purported Sender Domain. Mail servers or mail clients from Microsoft (such as Exchange or Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
The header field "X-MS-Exchange-Organization-SCL" is used by Microsoft Exchange Server and specifies the spam probability or trust level of the message. The value -1 indicates that the message originates from a trusted sender and is never treated as spam. The values 0 (low) to 9 (high) indicate the spam probability calculated from the message content. SCL stands for Spam Confidence Level. Mail servers or mail clients from Microsoft (such as Exchange or Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
The header field "X-MS-Exchange-Organization-SenderIdResult" is used by Microsoft applications and reports the results of a Sender-ID check. Mail servers or mail clients from Microsoft (such as Exchange or Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
ME4PR07MB0012The header "X-MS-Exchange-Transport-CrossTenantHeadersStamped" is used by Microsoft Exchange.
(Non-standard)
00:00:01.4742304The header "X-MS-Exchange-CrossTenant-Id" is used by Microsoft Exchange.
(Non-standard)
YesThe header field "X-MS-Has-Attach" is used by Microsoft applications and specifies that the message contains attachments if the value is "Yes". Mail servers or mail clients from Microsoft (such as Exchange or Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
Header fields beginning with "X-MS-Office365-" are usually inserted by Microsoft Office 365.
<225 ... 855@....EURP732.PROD.OUTLOOK.COM>The header field "X-MS-TNEF-Correlator" is created by Microsoft applications when creating a new TNEF message and contains the Message-ID of the parent message. TNEF stands for Transport Neutral Encapsulation Format. Mail servers or mail clients from Microsoft (such as Exchange or Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
NormalThe header field "X-MSMail-Priority" is used by Microsoft mail programs to specify the priority of the message. The value has no influence on the speed of transmission. This header is used in spam with a high priority value.
(Non-standard)
ExampleMailer 1.23The header file "X-Mailer" contains information about the software used to send the message. Usual information is the name and version number of the software, but also the URL or other information is possible.
(Non-standard)
The header field "X-Message-Flag" is used by Microsoft mail clients and can contain a custom text. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
Header fields beginning with "X-Microsoft-" are usually inserted by a Microsoft application.
(Non-standard)
UriScan:;BCL:0;PCL:0;RULEID:(7020095) ... (1701031045);SRVR:DB9EUR03HT123;The header "X-Microsoft-Antispam" is used by Microsoft Office 365 and contains information on spam protection, such as the phishing rating ("PCL:").
(Non-standard)
Header fields beginning with "X-Microsoft-Antispam-" are usually inserted by Microsoft Exchange Online (Office 365) and contain information on spam and phishing protection.
(Non-standard)
The header field "X-Microsoft-ClassDesc" is used by Microsoft mail clients and contains a human-readable summary of each of the classification categories included in the header field "X-Microsoft-Classification". Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
The header field "X-Microsoft-ClassID" is used by Microsoft mail clients and contains the GUID that identifies the list of email classification categories used by a Message object. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
trueThe header field "X-Microsoft-ClassKeep" is used by Microsoft mail clients and indicates whether the message uses any classification categories. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
The header field "X-Microsoft-Classification" is used by Microsoft mail clients and contains a list of the classification categories to which this Message object has been assigned. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
trueThe header field "X-Microsoft-Classified" is used by Microsoft mail clients and indicates whether the contents of a message are regarded as classified information. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
Produced By Microsoft MimeOLE V16.4.3528.331The header field "X-MimeOLE" contains information about the Microsoft MimeOLE version.
(Non-standard)
The header field "X-Mittente" is used when sending messages with "La Posta Elettronica Certificata" (Italian Certified Electronic Mail).
$label1 MyTagThe header field "X-Mozilla-Keys" is used by Mozilla Thunderbird to store the tags assigned to the message by the user.
(Non-standard)
0005The header field "X-Mozilla-Status" is used by Mozilla Thunderbird to store the message status or properties of a message. For example, whether a message has been read or marked.
(Non-standard)
00000000The header field "X-Mozilla-Status2" is inserted by Mozilla Thunderbird.
(Non-standard)
ExampleNewsReader 1.23The header file "X-Newsreader" contains information about the software used to send the message. Usual information is the name and version number of the software, but also the URL or other information is possible.
(Concerns Mail, concerns Netnews/Usenet, non-standard)
YesThe header field "X-No-Archive" indicates that the message should not be included in a public archive.
(Non-standard)
webmaster@domain.tldThe header field "X-Original-To" contains the original recipient of the message.
The header field "X-OriginalArrivalTime" contains the time when this message was delivered into the message transport system (usually the same time as in the last "Received" header field).
(Non-standard)
10.1.2.3The header field "X-Originating-IP" contains the IP address of the client when using the HTTP frontend of a mail service (Web-Mail). Since the HTTP frontend is the client for the SMTP server the IP of the HTTP frontend is recorded in the "Received" header field. The header field "X-Originating-IP" is used to identify the client of the HTTP frontend.
(Non-standard)
2.6.2 Subject,Control,Message-ID,Date,From,Sender iQCVAw ... srA=The header field "X-PGP-Sig" starts with the PGP version number from the signed output, then has the signed headers separated by commas (no spaces), and finally has the signature.
(Concerns Netnews/Usenet)
The header field "X-PMFLAGS" is inserted by Pegasus Mail into sent messages.
The header field "X-Payload-Class" is used by Microsoft mail clients and contains the class name of an object that can display the contents of the message. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
The header field "X-Payload-Provider-GUID" is used by Microsoft mail clients and contains the GUID of the software application that can display the contents of the message. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
SPAMThe header field "X-Phalanx-Mark" is inserted by the Phalanx Spam-Filter and contains the classification of the message as "SPAM" or "HAM".
(Non-standard)
3 rules matched: RULE_OFFER, HTML_IMG_LINK, BAYESThe header field "X-Phalanx-Rules" is inserted by the Phalanx Spam-Filter and contains the matched rules.
(Non-standard)
305The header field "X-Phalanx-Rules" is inserted by the Phalanx Spam-Filter and contains the message score. A value above 50 is more likely to be spam than non-spam.
(Non-standard)
3 (Normal)The header field "X-Priority" indicates the priority of the message. The value has no influence on the speed of transmission. Possible values are: 1 (Very high), 2 (High), 3 (Normal), 4 (Low), 5 (Very low). Sometimes only the number is used. This header is used in spam with a high priority value.
The header field "Envelope-To" contains the recipients from the SMTP envelope ("RCPT TO").
(Non-standard)
from sender.tld (sender.tld [10.1.2.3]) by server.tld with SMTP; 4 Oct 2019 15:40:53 +0200The header field "X-Received" contains information about the sender, the receiver and the received time of a message. This header is added by the receiving mail server as the top line. This header field is mostly used in internal networks.
(Non-standard)
abuse@domain.tldThe header field "X-Report-Abuse" contains the address to which complaints about an e-mail received can be addressed.
(Non-standard)
abuse@domain.tldThe header field "X-Report-Abuse-To" contains the address to which complaints about an e-mail received can be addressed.
(Non-standard)
The header field "X-Ricevuta" is used when sending messages with "La Posta Elettronica Certificata" (Italian Certified Electronic Mail).
The header field "X-Riferimento-Message-ID" is used when sending messages with "La Posta Elettronica Certificata" (Italian Certified Electronic Mail).
noname@example.tldThe header field "X-Sender" is used by some mail servers to enter the address given in the SMTP dialog ("MAIL FROM"). The POP or IMAP account name, to which no message can be sent, may also be entered by some mail servers.
3The header field "X-Sensitivity" indicates how sensitive it is to forward this message to people other than the specified recipients. Common values are "Personal", "Private", "Company-Confidential", "Internal" and "Normal". However, a number can also be specified as a value.
(Non-standard)
YesThe header field "X-Spam" is used by spam filters to specify the status of the message and/or the result of the filtering.
(Non-standard)
Header fields beginning with "X-Spam-" are usually inserted by spam filters.
(Non-standard)
SpamAssassin 3.4.0 (2014-02-07) on domain.tldThe header field "X-Spam-Checker-Version" is inserted by Apache SpamAssassin and contains, besides the program name, also the version number. There may be more information about how the release date or hostname was executed on SpamAssassin.
(Non-standard)
NOThe header field "X-Spam-Flag" contains the result of a spam check. The value is normally either "YES" (spam) or "NO" (no spam).
(Non-standard)
***The header field "X-Spam-Level" is inserted by Apache SpamAssassin. The number of asterisks ("*") corresponds to the integer part of the message score. If plus signs ("+") are added, they represent the number of tenths of the score value. For example, the characters "*******++" correspond to the score 5.2.
(Non-standard)
15.50/6.0 * -0.1 -- Forwarded email (Outlook style) * 0.9 -- From: ends in numbers ...The header field "X-Spam-Report" is inserted by Apache SpamAssassin and contains the result of the spam check. It starts with the score value of the message, followed by the score limit. Then follow the applicable rules and their respective scores.
(Non-standard)
-0.619The header field "X-Spam-Score" is inserted by Apache SpamAssassin and specifies the score value of the message. The higher this value, the more likely the message is to be spam. The score value can also be negative.
(Non-standard)
Yes, score=21.6 required=4.0 tests=BATMAIL,BAYES_99, DATE_IN_FUTURE_06_12, ... ,URIBL_WS_SURBL autolearn=spam version=3.2.1The header field "X-Spam-Status" is inserted by Apache SpamAssassin and contains the filter results. The value contains information about whether the message is spam (yes/no), the total score for the message (may be negative if it is whitelisted), and the score required to be classified as spam. This is followed by the comma-separated list of tests that returned a non-zero value. Finally, whether the message was automatically learned as spam or ham and the version of SpamAssassin.
(Non-standard)
Header fields beginning with "X-TM-" are usually inserted by Trend Micro products.
(Non-standard)
IMSS-7.1.0.1224-8.2.0.1013-24980.000The header field "X-TM-AS-Product-Ver" is used by Trend Micro products and contains, separated by hyphens, the product name, product version, anti-spam engine version, and virus definition (spam pattern) version.
(Non-standard)
No-1.618200-5.000000-10The header field "X-TM-AS-Result" is used by Trend Micro products and contains, separated by hyphens, the spam classification ("Yes" or "NO"), the score value (Trend Score), the spam detection threshold, the category and the type (Trend Type).
(Non-standard)
Match text exemption rules:NoThe header field "X-TM-AS-Result-Xfilter" is used by Trend Micro products and contains information for checking the text exception rules (X-Filter Check). If a message match a defined regular expression, it is not classified as spam.
(Non-standard)
1.0 aG9zdC5kb21haW4udGxk c2VuZGVyQGRvbWFpbi50bGQThe header field "X-TM-AS-SMTP" is used by Trend Micro products and contains the HELO and MAIL FROM information from the SMTP envelope received by the gateway filter. Both are separated by a space and each is Base64 encoded.
(Non-standard)
YesThe header field "X-TM-AS-User-Approved-Sender" is used by Trend Micro products and contains the result ("Yes" or "No") of the verification with the list of approved senders. If the sender matches an address in the approved senders list, the message will not be classified as spam.
(Non-standard)
NoThe header field "X-TM-AS-user-Blocked-Sender" is used by Trend Micro products and contains the result ("Yes" or "No") of the verification with the list of blocked senders. If the sender matches an address in the blocked senders list, the message will be classified as spam.
(Non-standard)
spf=pass (sender IP address: 10.1.2.3) smtp.mailfrom=domain.tld;The header field "X-TM-Authentication-Results" is used by Trend Micro products and contains the authentication results of a Sender Policy Framework (SPF) or DomainKeys Identified Mail (DKIM) verification.
(Non-standard)
The header field "X-TM-Deliver-Signature" is used by Trend Micro products and contains an MD5 hash value generated from the sender and message ID.
(Non-standard)
hGed94JSd ... dj/d8LR4dThe header field "X-TMASE-Version" is used by Trend Micro Anti-Spam Engine (TMASE) and contains vendor proprietary debug information.
(Non-standard)
10--16.285300-8.000000The header field "X-TMASE-Version" is used by Trend Micro Anti-Spam Engine (TMASE) and usually contains in most cases, separated by hyphens, the type (Trend Type), the score value (Trend Score) and the spam detection threshold.
(Non-standard)
1.486001.0001-0-1-16:0,44:0,22:0,12:1,39:0,32:0,35:0,50:0-0The header field "X-TMASE-Version" is used by Trend Micro Anti-Spam Engine (TMASE) Social Engineering Attack Protection (SNAP) and contains the result of the check. Separated by hyphens, it also contains the version number, the scan result and the aggressiveness level of the check.
(Non-standard)
SMEX-12.5.0.2039-8.5.1020-24982.005The header field "X-TMASE-Version" is used by Trend Micro Anti-Spam Engine (TMASE) and contains in most cases, separated by hyphens, the product name, product version, anti-spam engine version, and virus definition (spam pattern) version.
(Non-standard)
Header fields beginning with "X-TOI-" are usually inserted by T-Online.
(Non-standard)
123456::1234567890-0000A5C8-0C6F9BE3/0-0/0-0The header field "X-TOI-EXPURGATEID" is usually inserted by T-Online.
(Non-standard)
53c692d9-1234-5678-c3a4-7e55baf0002bThe header field "X-TOI-MSGID" is usually inserted by T-Online.
(Non-standard)
n;1;2024-01-01T12:00:00ZThe header field "X-TOI-SPAM" contains information about spam detection by T-Online.
(Non-standard)
CLEAN, NORMALThe header field "X-TOI-SPAMCLASS" contains information about spam detection by T-Online.
(Non-standard)
uncheckedThe header field "X-TOI-VIRUSSCAN" contains information about the anti-virus check by T-Online.
(Non-standard)
The header field "X-TipoRicevuta" is used when sending messages with "La Posta Elettronica Certificata" (Italian Certified Electronic Mail).
The header field "X-Trasporto" is used when sending messages with "La Posta Elettronica Certificata" (Italian Certified Electronic Mail).
4:xtdresult=NTUw ... MTsw,xtdcapabilitiesThe header field "X-UI-Application" is inserted by mail servers of United Internet (GMX, Web.de, 1&1 and some more).
(Non-standard)
notjunk:1;V03:K0:IAYZrhZLGH8=:Chj9OR ... GL8iF2bz=The header field "X-UI-Filterresults" is inserted by mail servers of United Internet (GMX, Web.de, 1&1 and some more) and contains the results of the spam filtering.
(Non-standard)
notjunk:1;V01:K0:CFCUBW ... 1gFe6The header field "X-UI-Out-Filterresults" is inserted by mail servers of United Internet (GMX, Web.de, 1&1 and some more) and contains the results of the spam filtering.
(Non-standard)
b1640dde-48d7-17be-28f0-84072f62da06The header field "X-UI-Application" is inserted by mail servers of United Internet (GMX, Web.de, 1&1 and some more).
(Non-standard)
0003419c47ba0615The header field "X-UIDL" contains the unique identifier of the message for the mail server. It is used for receiving messages via the Post Office Protocol (POP). In this way, the mail program avoids, for example, reloading a message that has already been downloaded.
The header field "X-URI" is sometimes used with the same meaning as "Content-Location", sometimes to indicate the web home page of the sender or of his organization.
(Non-standard)
The header field "X-URL" is sometimes used with the same meaning as "Content-Location", sometimes to indicate the web home page of the sender or of his organization.
(Non-standard)
The header field "X-VerificaSicurezza" is used when sending messages with "La Posta Elettronica Certificata" (Italian Certified Electronic Mail).
CheckedThe header field "X-Virus-Checked" is used to indicate that a virus scan has been performed.
(Non-standard)
amavisd-new at localdomainThe header field "X-Virus-Scanned" contains information about a virus scan. In most cases, the name of the software and the name of the checking host are specified. However, sometimes only the result, like "OK", is noted.
(Non-standard)
CleanThe header field "X-Virus-Status" is used to note the result of a virus scan. Sometimes the name of the anti-virus software is also noted.
(Non-standard)
CheckedThe header field "X-VirusChecked" is used to indicate that a virus scan has been performed.
(Non-standard)
The header field "X-VoiceMessageDuration" is used by Microsoft mail clients and specifies the length of the attached audio message, in seconds. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
The header field "X-VoiceMessageSenderName" is used by Microsoft mail clients and specifies the name of the caller who left the attached voice message, as provided by the voice network's caller ID system. Mail clients from Microsoft (such as Outlook) use this header field when converting Message objects used by Microsoft products to MIME messages.
(Non-standard)
The header field "X-X-Sender" is used by some mail servers to indicate an authentication of the sender which might not be usable to send e-mail to.
(Non-standard)
Header fields beginning with "X-antispameurope-" are inserted by a spam filter from Hornetsecurity GmbH (formerly antispameurope GmbH).
(Non-standard)
The header field "X-imss-scan-details" is used by Trend Micro products and contains the results for all spam or phishing filters, in the sequence by which the rules were applied.
(Non-standard)
The header field "X400-Content-Identifier" contains a text string that identifies the content of a message.
The header field "X400-Content-Return" indicates whether the content of a message is to be returned with non-delivery notifications.
The header field "X400-Content-Type" contains the X400 content type.
The header field "X400-MTS-Identifier" contains the X400 MTS-Identifier.
The header field "X400-Originator" contains the X400 Originator.
The header field "X400-Received" contains the X400 Received.
The header field "X400-Recipients" contains the X400 Recipients.
The header field "X400-Trace" contains the X400 Trace.
The header field "Xref" indicates where an article from the last news server was filed for editing. User agents often use the information in the Xref header to prevent the user from seeing the same article twice if it was sent to more than one newsgroup. This header field is also used by Microsoft applications and contains the name of the host and a white-space-separated list of colon-separated pairs of newsgroup names and message numbers.
(Concerns Netnews/Usenet)
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