SMTP (25)

smtp-user-enum

smtp-user-enum -U /usr/share/seclists/Usernames/top-usernames-shortlist.txt -t 192.168.229.56 -w 30

smtp-user-enum -U /usr/share/seclists/Usernames/xato-net-10-million-usernames-dup.txt -t postfish.offsec

also create your own dictionary to try with cewl.