My clients have been using their own smtp server (mail.theirdomain.com) to send mail for months and months without a problem. Then last night it just stopped working and they can't connect anymore. It basically times out. I've set up a test address and can confirm this.

Unfortunately, I have no other information to offer as I don't really know where to look. I'm hoping that somebody has had a similar problem and that it's an easy fix.

Any suggestions?

If you have a firewall disable it to test.

If they cannot connect maybe their isp started blocking?

Maybe just restart the mailserver, service exim restart, though if it works for you that is not going to do much.

Well, I think I've traced it down to the ISP.

From Bellsouth's website: "Port 25 filtering prevents spammers from sending waves of junk e-mail by preventing BellSouth.net email from being sent through mail servers not .net supported. With Port 25 filtering, anyone logged into a BellSouth.net access number or connected via a defined BellSouth IP Address can send e-mail through the .net mail servers only."

Of course, I tell all of my customers to use their ISP anyway. Heck, if you're paying for it you might as well use it! And while you're at it, take a load off the server too! Listening is another story...

Once they went to mail.bellsouth.net it worked.

Thanks!

Yeah thats what I figured, ISPs are starting to do that because a lot of the new viruses/worms are setup to start spamming. If the cable/dsl companies block it like that then a lot less spam would most likely end up being sent out As long as they keep providing email servers to use I am happy.

If you want to work around it can always clieck that put exim on port 26 box