This document uses the following terms:
Augmented Backus-Naur Form (ABNF): A modified version of Backus-Naur Form (BNF), commonly used by Internet specifications. ABNF notation balances compactness and simplicity with reasonable representational power. ABNF differs from standard BNF in its definitions and uses of naming rules, repetition, alternatives, order-independence, and value ranges. For more information, see [RFC5234].
AUTH command: A Post Office Protocol 3 (POP3) optional command that is used to send authentication information as specified in [RFC1734]. The "mechanism" name defined in the RFC is NTLM. The structure of the AUTH command as used in the POP3 AUTHentication Command Protocol Extension is as follows: "AUTH NTLM<CR><LF>".
NT LAN Manager (NTLM) Authentication Protocol: A protocol using a challenge-response mechanism for authentication in which clients are able to verify their identities without sending a password to the server. It consists of three messages, commonly referred to as Type 1 (negotiation), Type 2 (challenge) and Type 3 (authentication).
NTLM AUTHENTICATE_MESSAGE: The NTLM AUTHENTICATE_MESSAGE packet defines an NTLM authenticate message that is sent from the client to the server after the NTLM CHALLENGE_MESSAGE is processed by the client. Message structure and other details of this packet are specified in [MS-NLMP].
NTLM CHALLENGE_MESSAGE: The NTLM CHALLENGE_MESSAGE packet defines an NTLM challenge message that is sent from the server to the client. NTLM CHALLENGE_MESSAGE is generated by the local NTLM software and passed to the application that supports embedded NTLM authentication. This message is used by the server to challenge the client to prove its identity. Message structure and other details of this packet are specified in [MS-NLMP].
NTLM message: A message that carries authentication information. Its payload data is passed to the application that supports embedded NTLM authentication by the NTLM software installed on the local computer. NTLM messages are transmitted between the client and server embedded within the application protocol that is using NTLM authentication. There are three types of NTLM messages: NTLM NEGOTIATE_MESSAGE, NTLM CHALLENGE_MESSAGE, and NTLM AUTHENTICATE_MESSAGE.
NTLM NEGOTIATE_MESSAGE: The NEGOTIATE_MESSAGE packet defines an NTLM negotiate message that is sent from the client to the server. The NTLM NEGOTIATE_MESSAGE is generated by the local NTLM software and passed to the application that supports embedded NTLM authentication. This message allows the client to specify its supported NTLM options to the server. Message structure and other details are specified in [MS-NLMP].
NTLM software: Software that implements the NT LAN Manager (NTLM) Authentication Protocol.
POP3 response: A message sent by a POP3 server in response to a message from a POP3 client. The structure of this message, as specified in [RFC1939], is as follows: <+OK> <response text><CR><LF> or <-ERR> <response text><CR><LF>.
Security Support Provider Interface (SSPI): An API that allows connected applications to call one of several security providers to establish authenticated connections and to exchange data securely over those connections. It is equivalent to Generic Security Services (GSS)-API, and the two are on-the-wire compatible.
MAY, SHOULD, MUST, SHOULD NOT, MUST NOT: These terms (in all caps) are used as defined in [RFC2119]. All statements of optional behavior use either MAY, SHOULD, or SHOULD NOT.