TCP
21 FTP
22 SSH
25 SMTP
26 SMTP (Alternative port, configurable via WHM)
80 HTTP
110 POP3
143 IMAP
443 HTTPS
465 SMTPS
993 IMAP4
995 POP3
2082 cPanel (NON Encrypted)
2083 cPanel (HTTPS)
2086 WHM (NON Encrypted)
2087 WHM (Encrypted)
2095 Webmail (NON Encrypted)
2096 Webmail (Encrypted)
3306 MySQL (Only if allowing Remote Connections)

–UDP
53 DNS

It should be noted that if you’re firewalling off your server, you should open up a portrange for the FTP PassivePort Rolloff. Typically these are higher up ports and a wide range, such as 30000-50000. You’ll also need to modify your FTPd configuration to use this portrange as well. If you don’t, you’ll see issues with FTP connections dropping, successful logins, but a hang, pause or delay when dong an ls or beginning a transfer that results in a dropped connection. Typically this will affect ftp clients that are behind a firewall/router doing NAT translations.

Anyway, that’s it, quick and simple. Enjoy