SMTP Enumeration - Mail Severs

• Verify SMTP port using Netcat

  nc -nv $ip 25

Check for SMTP open relay

Check for email spoofing

Check for username enumeration using VRFY command

Banner grabbing and finding publicly known exploits

Send modified cryptors and check if SMTP gateway is enable to detect and block it?

Run all nmap script using following command: nmap -Pn -sS -p25 --script smtp* -v

SMTP

VRFY username (verifies if username exists – enumeration of accounts)
EXPN username (verifies if username is valid – enumeration of accounts)