1.7 Versioning and Capability Negotiation

This document covers versioning issues in the following areas:

  • Security and Authentication methods: The NTLM POP3 Extension supports the NTLMv1 and NTLMv2 authentication methods, as specified in [MS-NLMP].

  • Capability Negotiation: POP3 does not support negotiation of which version of the NTLM authentication protocol to use. Instead, the NTLM authentication protocol version is configured on both the client and the server before authentication. NTLM authentication protocol version mismatches are handled by the NTLM Authentication Protocol implementation, not by POP3.

The client discovers whether the server supports NTLM AUTH through the AUTH command, issued without any arguments, at which point the server responds with a list of supported authentication mechanisms followed by a line that contains only a period (.). If NTLM is supported, the server includes the word "NTLM" in the list.