I decided to switch to using the web interface for mail, exclusively. This was working fine without me having to do anything, but I didn't have access to my archive of old mail. So I decided to copy all of my old mail so I would easily be able to search through it.
The steps weren't exactly straight forward, but this is what worked for me:
- Created a Smart Mailbox that contained all of the mail sent or received before I started using Google Apps.
- Saved the messages into a single mbox
- Send the messages with GMail Loader.
There was one issue that I encountered was that I tried to have the messages sent through my hosting provider. It has a 1000 daily outbound smtp limit. So it took about 6 days for all of the messages to be received. (I should have read the documentation for GMail Loader, and there are instructions to avoid this problem.)