SMTP map uses fingerprinting to scan for the version of SMTP server software which is running on a machine.
You can download it from the following link: https://packetstormsecurity.com/files/download/30602/smtpmap-0.8-beta.tar.gz
Source: https://packetstormsecurity.com/files/30602/smtpmap-0.8-beta.tar.gz.html