GMail for Google Apps
Here’s something I noticed when setting up my Google Apps to have GMail work with my own domain.
When you’ve added a domain through the Google Apps dashboard, the following step is to setup MX records, the dns records that make e-mail go to where it’s supposed to be. Google instructs you to setup the following MX records (or very similar) in your domain host:

It’s clear enough and it worked flawlessly on my previous domain server. On the one I’ve been claiming my most recent domain names (like the one you’re visiting right now, mlagerberg.com), it did not. Now I’m not sure if this goes for more domain servers, so I can only say that I had to do the following on my host, which is iwantmyname.com.
Here’s how I fixed this: convert all the MX server addresses in the table to lowercase, and remove the dot at the end.
I honestly don’t know why that fixed it, but it did, and I hope it’s of any use for others with the same problem.