Michiel Bijland

Redirecting SMTP

August 16th, 2007

Due to my new appartement I have a new ISP, like all of them reroutes every connection on port 25 to it’s own smtp server. This is fine if you use their e-mail service but not if you are a domain owner or small company that just wants to use it’s own mail server. Today I fixed this issue in 10 minutes using rinetd on a server of mine, it redirects tcp traffic from one port to another, bypassing port 25 until I’m past my isp network.

The setup is quite simple:

1. apt-get install rinetd
2. note down, server ip and destination ip(mail server)
3. add your redirect line according to format
4. restart rinetd
5. all, done.

This is of course if you are running ubuntu or debian on your server, but for other distros it should be almost as simple.