7. Interaction with SMTP Extensions

The following table lists the current standards-track and Experimental SMTP extensions. Listed are the EHLO keyword, name, an indication as to the use of the extension on the submit port, and a reference:

Keyword        Name                        Submission  Reference
----------     --------------------------  ----------  ----------------
PIPELINING     Pipelining                    SHOULD    [PIPELINING]
ENHANCEDSTATUSCODES  Enhanced Status Codes   SHOULD    [CODES-EXTENSION]
ETRN           Extended Turn                 MUST NOT  [ETRN]
 ...           Extended Codes                SHOULD    [SMTP-CODES]
DSN            Delivery Status Notification  SHOULD    [DSN]
SIZE           Message size                  MAY       [SIZE]
 ...           521 reply code                MUST NOT  [521REPLY]
CHECKPOINT     Checkpoint/Restart            MAY       [CHECKPOINT]
BINARYMIME     Binary MIME                   MAY       [CHUNKING]
CHUNKING       Chunking                      MAY       [CHUNKING]
8BITMIME       Use 8-bit data                SHOULD    [8BITMIME]
AUTH           Authentication                MUST      [SMTP-AUTH]
STARTTLS       Start TLS                     MAY       [Start-TLS]
NO-SOLICITING  Notification of no soliciting MAY       [Msg-Track]
MTRK           Message Tracking              MAY       [Msg-Track]

Future SMTP extensions SHOULD explicitly specify if they are valid on the Submission port.

Some SMTP extensions are especially useful for message submission:

Extended Status Codes [SMTP-CODES] SHOULD be supported and used according to [CODES-EXTENSION]. This permits the MSA to notify the client of specific configuration or other problems in more detail than the response codes listed in this memo. Because some rejections are related to a site's security policy, care should be used not to expose more detail to unauthenticated senders than is needed

[PIPELINING] SHOULD be supported by the MSA.

[SMTP-AUTH] allows the MSA to validate the authority and determine the identity of the submitting user and MUST be supported by the MSA.

Any references to the DATA command in this memo also refer to any substitutes for DATA, such as the BDAT command used with [CHUNKING].