I got this using: telnet public-ip
telnet: Unable to connect to remote host: No route to host
and I got this using nmap -sS public-ip
PORT STATE SERVICE
25/tcp open smtp
80/tcp open http
110/tcp open pop3
143/tcp open imap
443/tcp open https
465/tcp open smtps
587/tcp open submission
993/tcp open imaps
995/tcp open pop3s