Starting early this morning I was unable to send any email from my Mac. Late this afternoon, my wife said she had the same problem. I did some testing and determined that I couldn’t send to any SMTP host (not just Comcast’s host) on port 25. I could send email from my Gmail account, but that’s browser based. I did a little surfing and found a thread on Chris Pirillo’s site in which others have had the same problem.

It turns out that Comcast has blocked my outbound traffic to port 25 on any server. Did they inform me? No. Was there a reason for doing so? No. I use the smtp.comcast.net server for outbound mail, as they told me to when I signed up for their service years ago.

I called Comcast support and spoke to a useless tech. He said I should call Apple because there must be a problem with my Mail program. Oh, and my wife’s, too, of course. But the Lockergnome thread suggested I call Comcast’s security department at 856-317-7272, which turned out to be a good idea. The first thing the automated system tells you to do is go to www.comcastsupport.com/alternateport and download the OneClick fix. Okay, except it’s specific to Outlook Express. Doh! Another call to the security guys to talk to real people. These folks at least know what they’re talking about, and I was able to get back up and running.

Apparently, this is part of some ongoing program. Comcast disables outbound traffic to port 25 at the drop of a hat. Other ISPs do this, too, although I would hope they’d communicate first with their customers. The fix?

1. Configure outbound email to smtp.comcast.net, but on port 587, not the default port 25.
2. You must use password authentication for outbound/SMTP. Unless you’re using your ISP’s web mail, you probably forgot your username and password, so you’ll have to call the ISP to get them.
3. Do not use SSL.

Alternatively, just do what so many people are doing and use Gmail.