May of 2009 I posted a blog on how to Setup Exchange 07 using a Dynamic IP (click here to read it). In this article I suggested a paid email relay service. At the time I was not able find a free email relay but now I have found a free email relay service. This service is www.mxguarddog.com.
It is not only email relay but a SPAM filter as well. I stumbled upon this looking for a free SPAM filter service for one of my clients. The nice thing about this relay service is they will forward to a different port. So the relay will accept mail on port 25 and relay it to your email server on whatever port you choose. This is helpful for anyone that has an ISP that blocks incoming traffic on port 25.
The way MX Guard Dog keeps this service free is by exchanging licenses for links on websites. They give you licenses depending on the amount of traffic the website you put the link on gets. For example I signed up for the service when I found it and put a link on my blog. They gave me 40 licenses for this. It’s a pretty sweet deal.