The following are the ports you may need if you are setting up an email client like: Thunderbird, Outlook, or Apple Mail to connect to your Cpanel/WHM server. The ports for Secure POP3 is 995, the port for Secure IMAP is 993, and outgoing port for Secure SMTP is 465.
Below is a list of the most common Cpanel/WHM email ports used (including non-SSL ports):
Secure POP3 (with SSL enabled): 995
Secure IMAP (with SSL enabled): 993
Secure STMP (with SSL enabled): 465
Alternate SMTP: 26
Alternate SMTP: 587
Secure Webmail (with SSL): 2096