Port 25 and Problems Sending Email

In addition to the physical ports (connection points) on the body of your computer, there are 65,000+ virtual ports that Windows recognizes. Port 25 has been defined as the standard port for sending email messages when your mail propgram uses protocols like POP3.

In an effort to reduce the amount of spam (junk email) being sent through their systems, many ISPs (Internet Service Providers) have begun blocking access to Port 25, thereby forcing email programs to use Port 587, which is the port for authenticated email. When using this port, Outlook must be configured for authentication, and your mail server must as well.

Note: The procedures for configuring mail that I provide here at Living With Outlook are configured for authentication.

On this site, you may run into the Port 25 issue when configuring Outlook to work with Yahoo! mail or NetZero Megamail. If you do, you will know because you will have followed all the steps properly, but Outlook won't be able to send the test message.

If that happens, work through the procedures again until you get to the Advanced tab. There, change the number in the Outgoing server (SMTP) field to 587, then complete the rest of the steps.

This should resolve the problem.