Topic: HOWTO: Delivering Email and Beating Spam Filters
I've been putting a pretty extensive post together on making sure delivered email isn't marked as spam. A lot of it is just a compilation of tips and best practices, but the heart of the tutorial is setting up dkimproxy to digitally sign emails with Domain Keys and DKIM.
The signing process I had the most trouble with as a lot of the information out there was conflicitng or out of date. While most of the information is language agnostic, I was working in Rails on a Ubuntu Hardy slicehost install and web app code examples are in Rails. I'm not sure what the protocol is on posting tutorial information here vs. linking to a blog, but my blog doesn't have any ads or anything and I'd rather not retype everything.
The first two parts are up. There will probably be two more, one dealing with setting up postfix with dkimproxy and one for configuing dkimproxy with all the dns stuff. I am striving for thoroughness, so if you have anything to add, please let me know.