telnet
telnet 192.168.1.1 25
vrfy [email protected]
存在返回220
不存在返回550
metasploit
>use auxiliary/scanner/smtp/smtp_enum >show options >set rhosts 192.168.1.1 >set user_file users.txt >run
smtp-user-enum
smtp-user-enum -M VRFY -U users.txt -t 192.168.1.1
ismtp
ismtp -h 192.168.1.1:25 -e ismtp-users.txt