Maria’s Guides

What to do if your ISP blocks Port 25.

A few months ago, I was suddenly unable to send e-mail from my computer. And I hadn’t changed a thing.

The problem wasn’t just my desktop computer. It was also my laptop and my husband’s laptop. The computers could receive e-mail. And they could access the Web. They just couldn’t send e-mail using Mail (on my Macs) or Outlook (on my husband’s PCs).

What did all of these computer have in common? They were all accessing the Internet through the same connection with the same ISP.

Information from Our ISP

A phone call cleared matters up. Our ISP had decided to block Port 25 on its server. It did this to prevent its customers from using their accounts to send massive amounts of spam. (Don’t ask me to explain how a port change can prevent this. I don’t know, mostly because I don’t need to know.) Since our e-mail client software used 25 to access the SMTP servers for our various e-mail accounts, we could no longer send mail.

Of course, if we were using the e-mail accounts provided with our Internet access on our ISP’s server, this would not have been a problem. That’s probably why they didn’t contact us to let us know we might have a problem. Either that or they simply don’t have our e-mail addresses — which is far more likely. So we learned about the ISP configuration change by it causing a problem.

Our ISP made three suggestions for a fix:

• Use the e-mail account on the ISP’s server that came with our account. Obviously, this was not acceptable. I already have a half-dozen active e-mail accounts; what makes these people think I want to add another?
• Use the Webmail access that might be part of our e-mail accounts on other servers. Again, this was asking for a lot. If you’ve ever been forced to use a Web-based e-mail client when you regularly use a mail application like Mail or Outlook, you know what I mean.
• Change the port for the outgoing mail server in our mail applications. This was the answer we needed. And with a little experimentation, I found the right solution.

Making Changes in Mail

Here are the step-by step instructions if you’re using Mail on a Mac. If you’re not a Mail user, you should be able to translate these instructions for your own e-mail application — even if that app is on a Windows PC.

1. Open Mail.
2. Choose Mail > Preferences to open the Preferences dialog.
3. Click the Accounts button at the top of the window to access account settings. Make sure the Account Information pane is displayed as shown here. (I told you I had a lot of e-mail addresses.)
   
4. Select the e-mail account you want to modify.
5. Click the Server Settings button near the bottom of the pane to display a dialog sheet of SMTP server settings (shown here).
6. Change the Server Port value as follows:
   • For a POP server, enter 80.
   • For an IMAP server (including a .Mac account), enter 587.

   Do not change any other setting in the dialog!

7. Click OK to save the setting and close the dialog sheet.
8. Repeat steps 4 through 7 for each account you need to change. (It’ll likely be all of them.) When prompted to save changes in an account, be sure to click Save.
9. When you are finished making changes, click the Close button in the Accounts (Preferences) window to dismiss it. Be sure to click Save if prompted to save changes for the last account you changed.

Although I’m not sure if it’s necessary, restarting Mail might be a good idea. Quit it and start it again. It should work from that point forward.

Of course, these instructions assume that there are no other changes to the system and the other settings were working and are correct. If you can’t get this to solve your problem, get on the phone with your ISP’s technical support team. (Please don’t ask me to troubleshoot your Internet connection issues!)

Oh, and please don’t attempt to hack into my server with the settings you see in the images here. I’ve modified them so they simply won’t work, even if you did manage to guess my password.

Bonus Tip

Ever have the same problem sending e-mail from your laptop when using someone else’s WiFi service, like in a hotel or cafe? It’s likely the same issue: a lockdown of port 25 on that ISP’s system. Following these steps can get around it.