An updated internet-draft is available from the IETF.
Abstract: «This document defines a profile of the Simple Authentication and Security Layer (SASL) for the Post Office Protocol (POP3). This extension allows a POP3 client to 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. »
«In order to consolidate all of the authentication related information for POP3 into a single document, this document obsoletes RFC1734 and RFC3206, replacing them as a Proposed Standard. It also updates information contained in Section 6.3 and Section 8 of RFC2449.»