They Blocked My SMTP, Now What?

mindsuck asks: "As of this Wednesday, my ISP blocked my port 25, leaving my mailserver useless to the outside world as a consequence of spammers and their nasty worms. So I decided to ask the nice people of Slashdot. What can I do now to restore my smtp service, besides changing ISPs, is there a obscure way to run a mailserver off a non-standard port? What about services similar to those provided by dyndns.org for this kind of situations? Pros and Cons of using this services? Should I move my MX to a more 'stable' server than my homegrown one?" This topic was last touched upon in this article, from 2002. It's been over a year since SMTP blocks have become commonplace. Have you noticed a slowdown in your SPAM? Are ISP SMTP blocks really helping the problem? Updated: It looks like Charter is also blocking SMTP. Might there be a way to work with your ISP to get them to unblock port 25 for you, if you can sufficiently satisfy them that you are not a spammer?

Krondor wrote in with a similar query: "Charter Communications (in my area) has blocked outbound SMTP connections. I need to be able to send Email to other SMTP servers, besides theirs, for a number of legitamate reasons. My question is this; How can I either still send SMTP to the places I need to, or how can I convince Charter to unblock outbound SMTP (I can understand blocking inbound SMTP without ACK bit set)? They do provide a relay, but won't my messages get labelled as SPAM if I use that? I am also concerned because, this relay is not encrypted with SSL and I don't necessarily trust Charter with that."

Comments

Use your ISP for SMTP or change ISP

[Captain Kirk]

If you want a practical service it MUST be port 25. If you can't offer port 25, either you need to use someone else's smtp server or to change ISP.

Move to SMTP over SSL

[reaper20]

... and then use a smarthost (another box that sends mail on your behalf) to send the mail for you. I haven't heard of anyone blocking SMTP-SSL.

This sucks because you need a box outside your network to do this .... but if you got a few buddies with your own mailservers you can chip in on one on a host somewhere, or find a trustworthy friend that will let you relay.

Not the perfect solution but you at least get _some_ semblance of control.

Re:I wish more of them would

[grunthos]

my ISP blocked my port 25

Incoming, outgoing, or both? The workarounds can be different depending on which it is.

And yes you can run it on non-standard ports. 26 is fairly common.

Except that the great wide world can't send mail to you if you're listening there. The sender has to be specifically configured for that.

One thing I'm doing as a backup to my main connection is (everybody get ready to cringe) UUCP over TCP port 540. It's an easy config in the Unix/Linux world with Taylor UUCP. Sendmail handles it fine. No, no bang paths-- just plain domain names.

This would be a workaround for a problem on incoming mail. In my case, my primary MX record points to my mail server, and my secondary MX points to my UUCP relay site (bungi.com). If a sender can't connect to me, they go to the secondary where it queues. I run an hourly UUCP poll over TCP, which picks up anything waiting. If my main connection went down or were blocked, I could retrieve incoming mail with any generic PPP dial-up account.

I know, sounds kludgy, but it works fine.

This would work as a workaround for outgoing blockage also, but it would be much easier to use your ISP's outgoing mail server.