What port is recommended for secure SMTP communications between client and mailserver.

What port is recommended for secure SMTP communications between client and mailserver.

• 587
• 965
• 465
• 25 

 

EXPLANATION

Port 465 was never recognized by the IETF (Internet Engineering Task Force), as an official port for SMTP and has been assigned to another service.
Port 25 can be used but alot of ISP's block this due to the prevalence of unsecured mail servers on this port and the spam sending capabilities this exposes. Port 965 is your POP3 (receive) port, so while it is the correct POP3 port it shouldn't be used for SMTP (send).

SOURCE

https://www.jscape.com/blog/smtp-ports