1.4 Relationship to Other Protocols
The NTLM POP3 Extension uses the POP3 AUTH extension mechanism, as specified in [RFC1734], and is an embedded protocol. Unlike stand-alone application protocols, such as Telnet or HTTP, packets for this specification are embedded in POP3 commands and server responses.
POP3 specifies only the sequence in which a POP3 server and POP3 client are required to exchange NTLM messages to authenticate the client to the server successfully. It does not specify how the client obtains NTLM messages from the local NTLM software, or how the POP3 server processes NTLM messages. The POP3 client and POP3 server implementations depend on the availability of an implementation of the NTLM Authentication Protocol (as specified in [MS-NLMP]) to obtain and process NTLM messages and on the availability of the base64 encoding and decoding mechanisms (as specified in [RFC2045]) to encode and decode the NTLM messages embedded in POP3 packets.
For conceptual background information and overviews of the relationships and interactions between this and other protocols, see [MS-OXPROTO].