Friday, January 30, 2009

Comcast blocking incoming port 25 (SMTP)

I’ve run my own mail server in my house for quite a long time now, with no problems, no downtime, and it just works. Not anymore… Comcast has finally gotten around to my account to block my incoming port 25. As far as I can tell this started at midnight Thursday morning.
Several years ago they blocked my outgoing port 25, unless I used the Comcast MTA. That’s OK… so that’s what I did, reconfigured my postfix to use their MTA. But now that doesn’t even work—until I change it to use port 587.
A call to customer support gives you the expected response: “Are you using XP or Vista?” “You can’t read email in Outlook?” Of course, none of this is relevant. When the tech support person carries the appropriate information to the supervisor, the expected response is received: this is the policy for Comcast subscribers and there’s no option around it.
But there are still options… Here’s my list that I’ve been considering:
  • Plead with Comcast Has anyone had success with this approach?
  • Switch ISP There really aren’t many options here in the Bay Area. I’ve tried AT&T, other medium sized and smaller DSL’s, and they all have their disadvantages, including blocking port 25. But I am forever hopeful that someday we’ll get Fiosand they’ll be good enough not to do port blocking or other evil ISP things.
  • This is the service I’ve been using for 12 years now. They forward my email address to one that I specify. Until yesterday that was an address on a machine in my closet. Now I have it forwarded to gmail. I’ve asked them if they can forward to a port other than 25, but I haven’t gotten a response yet…
  • No-IP This is a little different than You point your MX record at their servers and they “reflect” the email right into your server with whatever address and port you give them. This costs $40 a year… The benefit over is that I can use this for whatever email address I like with my own domain. There are other vendors, such as AuthSMTP and DynDNS (which I use for DNS), and there’s a list that’s slightly out of date here.
  • GMail I can just stick with GMail and be done with it. You can find lots of discussions about using GMail, or any free email service. I just would have preferred to have some control over my own data… Update: I discovered that gmail is rewriting my outgoing email address with (this is a problem because I want everyone to remember my “permanent” address at which is forwarded to gmail); but, you can actually teach gmail your intended email address. I saw this tip in this lifehacker article.


  1. Well, your pain is now my pain. Apparently Comcast has turned off port 25. So much for training up on Exchange 2013. Have you been satisfied with your alternate solutions?

    1. Yep, my alternate solution is GMail. It is awesome, and I just don't worry about my email anymore.

      Although it sure would be nice to have options... Ultimately the lack of options here is due to the lack of ISPs in the Bay Area.