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. Most of them are available for general use, but several have uses that are more or less industry standards.

Port 25 has been defined as the standard port for sending email messages when your mail program uses protocols like POP3. This used to work great, but now there's a problem. Scammers, spammers, and assorted other lowlifes started using other people's Port 25 connections to do their dirty work.

In an effort to reduce the amount of spam and so on being sent through their systems, many ISPs (Internet Service Providers) have begun blocking access to this port, thereby forcing email programs to use Port 587, which is the port for authenticated email. This prevents the bad guys from getting in to the email servers while allowing legitimate users to work normally. As long as your email program and the mail server are both configured to use Port 587, everything is great.

But legitimate users can get messed up when your mail program isn't using the same port as the ISP. A lot of ISPs are switching to Port 587.

If your ISP switches and you don't, you'll suddenly find that you can't send email any more. Or if you are setting up a new email account with old directions that assume the use of Port 25, you may find that you can receive email but cannot send email.

What to Do

Happily, fixing this problem isn't too tough. You need to go to the technical support website for the ISP, and search for instructions on configuring your email program to work with their email servers. Those instructions should always be current, and tell you the correct port to use.

Outlook Users

If you find that your existing Outlook setup can no longer send emails when it could before, your ISP has probably reconfigured for authentication. Or if you are setting up a new email account and it seems that you did everything right, but Outlook won't send the test message, you are probably running into this problem.

The procedures for configuring email that I provide here at Living With Outlook assume that you will need to use authentication. So if you ran into a problem and are using Yahoo! Mail or NetZero Megamail, work through the procedures I've included here 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.

Return from this Port 25 page to the Mail Tips page.
Return from this Port 25 page to the "Can't Send Email" page.