SMTP Service Extension for Authentication
RFC 4954

Received changes through RFC Editor sync (changed abstract to 'This document defines a Simple Mail Transport Protocol (SMTP) extension whereby an SMTP client may indicate an authentication mechanism to the server, perform an authentication protocol exchange, and optionally negotiate a security layer for subsequent protocol interactions during this session. This extension includes a profile of the Simple Authentication and Security Layer (SASL) for SMTP.

This document obsoletes RFC 2554. [STANDARDS-TRACK]')