The Post Office Protocol Version 3 (POP3) extensions specify extensions to the Post Office Protocol Version 3 (POP3). The following extensions are specified:
The NT LAN Manager (NTLM) authentication mechanism for the POP3 protocol. This is a proprietary extension that is used with the POP3 AUTH command.
The delegate access mechanism for the POP3 protocol.
For the purposes of this document, the NTLM authentication mechanism for POP3 is referred to in subsequent sections as "the NTLM POP3 Extension", and the delegate access mechanism for POP3 is referred to as "the POP3 Delegate Access extension".
Sections 1.8, 2, and 3 of this specification are normative and can contain the terms MAY, SHOULD, MUST, MUST NOT, and SHOULD NOT as defined in RFC 2119. Sections 1.5 and 1.9 are also normative but cannot contain those terms. All other sections and examples in this specification are informative.