MAIL Parameters

Last Updated
2014-07-07
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Registries included below

SMTP Service Extensions

Registration Procedure(s)
Standards-Track or IESG-Approved Experimental RFC
Reference
[RFC5321, Section 2.2]
Note
The Simple Mail Transfer Protocol [RFC5321] specifies a set of commands
or services and a general procedure for extending that set. The table
below lists SMTP service extensions. Both message submission [RFC6409]
and mail transfer [RFC5321] may use these extensions unless otherwise
specified.

As specified in [RFC5321] Section 2.2.2, no entry may be made in this
registry that starts in an "X". Entries may be made only for service
extensions (and associated keywords, parameters, or verbs) that are
defined in Standards-Track or Experimental RFCs specifically approved
by the IESG for this purpose.

The server response to a client EHLO command includes a keyword for
each service extension the server implements.  Some of these keywords
have parameters, which are listed in the "SMTP Service Extension
Parameters" registry.
Available Formats

CSV
EHLO Keyword Description Reference Note
SEND Send as mail [RFC821] The description of SEND was updated by [RFC1123] and then its actual use was deprecated in [RFC2821]
SOML Send as mail or to terminal [RFC821] The description of SOML was updated by [RFC1123] and then its actual use was deprecated in [RFC2821]
SAML Send as mail and to terminal [RFC821] The description of SAML was updated by [RFC1123] and then its actual use was deprecated in [RFC2821]
EXPN Expand the mailing list [RFC821] Command description updated by [RFC5321]
HELP Supply helpful information [RFC821] Command description updated by [RFC5321]
TURN Interchange the client and server roles [RFC821] The actual use of TURN was deprecated in [RFC2821]
8BITMIME SMTP and Submit transport of 8bit MIME content [RFC6152]
SIZE Message size declaration [RFC1870]
VERB Verbose [Eric Allman]
ONEX One message transaction only [Eric Allman]
CHUNKING Chunking [RFC3030]
BINARYMIME Binary MIME [RFC3030]
CHECKPOINT Checkpoint/Restart [RFC1845]
DELIVERBY Deliver By [RFC2852]
PIPELINING Command Pipelining [RFC2920]
DSN Delivery Status Notification [RFC3461]
ETRN Extended Turn [RFC1985] SMTP [RFC5321] only. Not for use on Submit port 587.
ENHANCEDSTATUSCODES Enhanced Status Codes [RFC2034]
STARTTLS Start TLS [RFC3207]
NO-SOLICITING Notification of no soliciting [RFC3865]
MTRK Message Tracking [RFC3885]
SUBMITTER SMTP Responsible Submitter [RFC4405]
ATRN Authenticated TURN [RFC2645] SMTP [RFC5321] only. Not for use on Submit port 587.
AUTH Authentication [RFC4954]
BURL Remote Content [RFC4468] Submit [RFC6409] only. Not for use with SMTP on port 25.
FUTURERELEASE Future Message Release [RFC4865]
UTF8SMTP Internationalized email address [RFC5336] Experimental; deprecated in [RFC6531].
CONPERM Content Conversion Permission [RFC4141]
CONNEG Content Conversion Negotiation [RFC4141]
SMTPUTF8 Internationalized email address [RFC6531]
MT-PRIORITY Priority Message Handling [RFC6710]
RRVS Require Recipient Valid Since [RFC7293]

SMTP Service Extension Parameters

Registration Procedure(s)
Standards-Track or IESG-Approved Experimental RFC
Reference
[RFC5321, Section 2.2]
Note
Some of the keywords in the "SMTP Service Extensions" registry have
parameters.  These are listed here (those keywords not listed here
have no parameters).
Available Formats

CSV
EHLO Keyword Parameters Reference
SIZE number [RFC1870]
NO-SOLICITING Soliciting-keywords [RFC3865]
AUTH SASL mechanism names [RFC4954]
BURL Permitted URL prefixes [RFC4468]
MT-PRIORITY Name of the Priority Assignment Policy (optional) [RFC6710]

Mail Transmission Types

Registration Procedure(s)
Standards-Track or IESG-Approved Experimental RFC
Reference
[RFC821][RFC822][RFC5321]
Note
The Simple Mail Transfer Protocol [RFC821][RFC5321] and the Standard for
the Format of ARPA Internet Text Messages [RFC822] specify that a set of
"Received" lines will be prepended to the headers of electronic mail
messages as they are transported through the Internet.
These received line may optionally include either or both a "via" phrase
and/or a "with" phrase.  The legal values for the phrases are listed here.
The via phrase is intended to indicate the link or physical medium over
which the message was transferred.  The with phrase is intended to
indicate the protocol or logical process that was used to transfer the
message.

VIA link types

Available Formats

CSV
VIA link types Description Reference
UUCP Unix-to-Unix Copy Program
TCP TCP [RFC5321]

WITH protocol types

Available Formats

CSV
WITH protocol types Description Reference
SMTP Simple Mail Transfer Protocol [RFC5321]
ESMTP SMTP with Service Extensions [RFC5321]
ESMTPA ESMTP with AUTH [RFC3848]
ESMTPS ESMTP with STARTTLS [RFC3848]
ESMTPSA ESMTP with both STARTTLS and AUTH [RFC3848]
LMTP Local Mail Transfer Protocol [RFC3848]
LMTPA LMTP with AUTH [RFC3848]
LMTPS LMTP with STARTTLS [RFC3848]
LMTPSA LMTP with both STARTTLS and AUTH [RFC3848]
MMS Multimedia Messaging Service [RFC4356]
UTF8SMTP ESMTP with SMTPUTF8 [RFC6531]
UTF8SMTPA ESMTP with SMTPUTF8 and AUTH [RFC4954][RFC6531]
UTF8SMTPS ESMTP with SMTPUTF8 and STARTTLS [RFC3207][RFC6531]
UTF8SMTPSA ESMTP with SMTPUTF8 and both STARTTLS and AUTH [RFC3207][RFC4954][RFC6531]
UTF8LMTP LMTP with SMTPUTF8 [RFC6531]
UTF8LMTPA LMTP with SMTPUTF8 and AUTH [RFC4954][RFC6531]
UTF8LMTPS LMTP with SMTPUTF8 and STARTTLS [RFC3207][RFC6531]
UTF8LMTPSA LMTP with SMTPUTF8 and both STARTTLS and AUTH [RFC3207][RFC4954][RFC6531]

Additional-registered-clauses

Registration Procedure(s)
Standards-Track or IESG-Approved Experimental RFC
Reference
[RFC5321]
Available Formats

CSV
Clause Name Description Syntax Summary Reference
PRIORITY Records the value of the MT-PRIORITY parameter specified in the MAIL FROM command See Section 7 of RFC [RFC6710]
state Indicates entry into a special queue state state <state-name> [RFC6729]

SMTP PRIORITY extension Priority Assignment Policy

Registration Procedure(s)
Specification Required
Reference
[RFC6710]
Available Formats

CSV
Policy Name Comment Reference
MIXER Default policy [RFC6710, Appendix B]
STANAG4406 [RFC6710, Appendix A]
NSEP [RFC6710, Appendix C]

Registered-states

Registration Procedure(s)
First Come First Served
Reference
[RFC6729]
Available Formats

CSV
Name Description Reference Use
auth Held for message authentication [RFC6729] current
content Held for message content analysis [RFC6729] current
convert Held for message content conversion [RFC6729] current
moderation Held for list moderation [RFC6729] current
normal Message is not being held other than to accommodate typical relaying handling [RFC6729] current
other Held for causes not covered by other registered state keywords [RFC6729] current
outbound Message placed in outbound queue [RFC6729] current
quarantine Held for operator action due to content analysis or local policy [RFC6729] current
timed Held to accommodate a specific requested delivery window [RFC6729] current