RFC 1854 (rfc1854) - Page 2 of 7

SMTP Service Extension for Command Pipelining

RFC 1854                    SMTP Pipelining                 October 1995


       until some intermediate point in the SMTP dialogue.
       When this is done material read from the TCP connection
       and kept in process buffers can be lost.

 (2)   Flushing the TCP input buffer when an SMTP command
       fails. SMTP commands often fail but there is no reason
       to flush the TCP input buffer when this happens.
       Nevertheless, some SMTP servers do this.

 (3)   Improper processing and promulgation of SMTP command
       failures. For example, some SMTP servers will refuse to
       accept a DATA command if the last RCPT TO command
       fails, paying no attention to the success or failure of
       prior RCPT TO command results. Other servers will
       accept a DATA command even when all previous RCPT TO
       commands have failed. Although it is possible to
       accommodate this sort of behavior in a client that
       employs command pipelining, it does complicate the
       construction of the client unnecessarily.

   This memo uses the mechanism described in [2] to define an extension
   to the SMTP service whereby an SMTP server can declare that it is
   capable of handling pipelined commands. The SMTP client can then
   check for this declaration and use pipelining only when the server
   declares itself capable of handling it.

1.  Framework for the Command Pipelining Extension

   The Command Pipelining extension is defined as follows:

    (1)   the name of the SMTP service extension is Pipelining;

    (2)   the EHLO keyword value associated with the extension is
          PIPELINING;

    (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.





Freed & Cargille            Standards Track