Table of header field registrations

Header name

Protocol

Date Mail Message date and time
From Mail Mailbox of message author
Sender Mail Mailbox of message sender
Reply-To Mail Mailbox for replies to message
To Mail Primary recipient mailbox
Cc Mail Carbon-copy recipient mailbox
Bcc Mail Blind-carbon-copy recipient mailbox
Message-ID Mail Message identifier
In-Reply-To Mail Identify replied-to message(s)
References Mail Related message identifier(s)
Subject Mail Topic of message
Comments Mail Additional comments about the message
Keywords Mail Message key words and/or phrases
Resent-Date Mail Date and time message is resent
Resent-From Mail Mailbox of person for whom message is resent
Resent-Sender Mail Mailbox of person who actually resends the message
Resent-To Mail Mailbox to which message is resent
Resent-Cc Mail Mailbox(es) to which message is cc'ed on resend
Resent-Bcc Mail Mailbox(es) to which message is bcc'ed on resend
Resent-Reply-To Mail Resent reply-to
Resent-Message-ID Mail Message identifier for resent message
Return-Path Mail Message return path
Received Mail Mail transfer trace information
Encrypted Mail Message encryption information
Disposition-Notification-To Mail Mailbox for sending disposition notification
Disposition-Notification-Options Mail Disposition notification options
Accept-Language Mail Language(s) for auto-responses
Original-Message-ID Mail Original message identifier
PICS-Label Mail PICS rating label
Encoding Mail Message encoding and other information
List-Archive Mail URL of mailing list archive
List-Help Mail URL for mailing list information
List-ID Mail Mailing list identifier
List-Owner Mail URL for mailing list owner's mailbox
List-Post Mail URL for mailing list posting
List-Subscribe Mail URL for mailing list subscription
List-Unsubscribe Mail URL for mailing list unsubscription
Message-Context Mail Type or context of message
DL-Expansion-History Mail Trace of distribution lists passed
Alternate-Recipient Mail Controls forwarding to alternate recipients
Original-Encoded-Information-Types Mail Body part types in message
Content-Return Mail Return content on non-delivery?
Generate-Delivery-Report Mail Request delivery report generation
Prevent-NonDelivery-Report Mail Non-delivery report required?
Obsoletes Mail Reference message to be replaced
Supersedes Mail Reference message to be replaced
Content-Identifier Mail Message content identifier
Delivery-Date Mail Message delivery time
Expiry-Date Mail Message expiry time
Expires Mail Message expiry time
Reply-By Mail Time by which a reply is requested
Importance Mail Message importance
Incomplete-Copy Mail Body parts are missing.
Priority Mail Message priority
Sensitivity Mail Message content sensitivity
Language Mail X.400 message content lenguage
Conversion Mail Conversion allowed?
Conversion-With-Loss Mail Lossy conversion allowed?
Message-Type Mail Message type: delivery report?
Autosubmitted Mail Automatically submitted indicator
Autoforwarded Mail Automatically forwarded indicator
Discarded-X400-IPMS-Extensions Mail X.400 IPM extensions discarded
Discarded-X400-MTS-Extensions Mail X.400 MTS extensions discarded
Disclose-Recipients Mail Disclose names of other recipients?
Deferred-Delivery Mail Deferred delivery information
Latest-Delivery-Time Mail Latest delivery time requested
Originator-Return-Address Mail Originator return address
X400-Content-Identifier Mail Message content identifier
X400-Content-Return Mail Return content on non-delivery?
X400-Content-Type Mail X400 content type
X400-MTS-Identifier Mail X400 MTS-Identifier
X400-Originator Mail X400 Originator
X400-Received Mail X400 Received
X400-Recipients Mail X400 Recipients
X400-Trace Mail X400 Trace