Archive for the 'SMTP' Category

Blocking Port 25

Posted in SMTP on May 14th, 2005 at 09:26:52

So, for the first time this weekend, I’m on a network where outgoing mail on port 25 is blocked. How annoying.

I use a number of mail servers in a number of different ways. Typically, when on one of my Linux boxes (zeus or athena) I’ll send mail directly from those servers by using a localhost Postfix installation, and no smart or relay hosts. I don’t really see a need for my ISP to see my mail, and doing it this way is the default setup for most Linux distros that I’m aware of.

If I’m someplace that doesn’t have a mail server (ie the powerbook, creusa, or the mac mini, hermes), I use athena as a mail host, on which I have installed SASL authentication. Athena is set up to accept mail in a couple cases:

1. Mail from local network. This includes all the IPs in my block on Sagonet.
2. SASL Authenticated users: This users password authentication against the local mail database to check users who can login to the server to send mail.

As such, the server is protected against being an open relay (so long as I don’t get a spammer on the local machine, but I don’t think that’s going to be the case), and I like having it there as a backup for when other mail servers fail me. wedu’s mail uses POP before SMTP for authentication, which is all well and good, but can be a pain since the logs are reset at :45 past the hour, and if you try and send mail right after that, you get a nice “Relay denied” message.

In any case, I tried to send mail this morning via… and got a timeout. Tried getting there from here, no go. Panicked a bit, since this is my main mail server, and if it’s down, that’s a bad thing. Tested it from zeus: no problems. Tested it locally: no problems. Tried going to another port 25… problems. So it’s on the Ameritech end. Great.

Set up an ssh tunnel: ssh -L 25:localhost:25 Set up a server in as localhost port 25. Forward my mail. Sigh at Ameritech. Bitch in weblog. And the circle of life continues.