We do not restrict any ports unless there is a security threat to our network or users.
Port 25 – Outgoing Email – Port 25 is closed for mail servers due to spam and security protection. Instead modern mail providers typically use port 587 or 465 with encryption enabled. Port 25 is considered old and is not used in most modern email systems.
Port 25 is used by the original SMTP protocol from 1981, this allows email to be sent in an unencrypted format and can be easily manipulated or intercepted. Instead most modern mail providers use a secure method that encrypts the connection and uses port 587 or 465 instead.