4 Protocol Examples

The following sequence diagram shows an example of an authentication exchange that uses the SASL_Mechanism_Supported message described in section 2.2.1. In this example, the client requests authentication using the NT LAN Manager (NTLM) Authentication: Simple Mail Transfer Protocol (SMTP) Extension, as described in [MS-SMTPNTLM].

Example authentication exchange

Figure 1: Example authentication exchange

  1. The initial response by the SMTP server ("220 SMTP.example.com") is the greeting by the server as specified in [RFC5321].

  2. The client sends the EHLO command.

  3. The server responds with, among other things, an indication of support for NTLM authentication.

  4. The client issues the AUTH NTLM command, omitting the initial response.

  5. The server responds with the SASL_Mechanism_Supported message.