This memo defines a framework for extending the SMTP service by defining a means whereby a server SMTP can inform a client SMTP as to the service extensions it supports. [STANDARDS-TRACK]| IETF Datatracker
This memo describes a low cost, deterministic means for messages to be identified as submissions, and specifies what actions are to be taken by a submission server. [STANDARDS-TRACK]| IETF Datatracker
This memo defines an extension to the SMTP service [RFC-821, RFC-1869] whereby an SMTP server augments its responses with the enhanced mail system status codes defined in RFC 1893. [STANDARDS-TRACK]| IETF Datatracker