RFC 2197 (rfc2197) - Page 3 of 8
SMTP Service Extension for Command Pipelining
Alternative Format: Original Text Document
RFC 2197 SMTP Service Extension September 1997
(3) no parameter is used with the PIPELINING EHLO keyword;
(4) no additional parameters are added to either the MAIL
FROM or RCPT TO commands.
(5) no additional SMTP verbs are defined by this extension;
and,
(6) the next section specifies how support for the
extension affects the behavior of a server and client
SMTP.
4. The Pipelining Service Extension
When a client SMTP wishes to employ command pipelining, it first
issues the EHLO command to the server SMTP. If the server SMTP
responds with code 250 to the EHLO command, and the response includes
the EHLO keyword value PIPELINING, then the server SMTP has indicated
that it can accommodate SMTP command pipelining.
4.1. Client use of pipelining
Once the client SMTP has confirmed that support exists for the
pipelining extension, the client SMTP may then elect to transmit
groups of SMTP commands in batches without waiting for a response to
each individual command. In particular, the commands RSET, MAIL FROM,
SEND FROM, SOML FROM, SAML FROM, and RCPT TO can all appear anywhere
in a pipelined command group. The EHLO, DATA, VRFY, EXPN, TURN,
QUIT, and NOOP commands can only appear as the last command in a
group since their success or failure produces a change of state which
the client SMTP must accommodate. (NOOP is included in this group so
it can be used as a synchronization point.)
Additional commands added by other SMTP extensions may only appear as
the last command in a group unless otherwise specified by the
extensions that define the commands.
The actual transfer of message content is explicitly allowed to be
the first "command" in a group. That is, a RSET/MAIL FROM sequence
used to initiate a new message transaction can be placed in the same
group as the final transfer of the headers and body of the previous
message.
Client SMTP implementations that employ pipelining MUST check ALL
statuses associated with each command in a group. For example, if
none of the RCPT TO recipient addresses were accepted the client must
Freed Standards Track