SMTP by default uses TCP port 25. The protocol for mail submission is the same, but uses port 587. SMTP connections secured by SSL, known as SMTPS, default to port 465 (nonstandard, but sometimes used for legacy reasons).
If you can’t send email and you’re using a commercial ISP , they may be blocking SMTP port 25. This port is standard for sending email. But it’s also standard for sending spam, so ISPs often block it. In order to send email again, you’ll have to change to a […]