One of the minor things I’ve noticed when I use Thunderbird on my IMAP accounts is that it doesn’t download IMAP messages until I click on them. Then I have to wait until I can see the message. I have heard that this is supposed to be fixed in Thunderbird 3, and I tried it but a lot of the extensions I need aren’t compatible with it.
Today I finally tried to search and find out more about the problem. Turns out I’m not alone — others have noticed that the setting to download message bodies for offline use doesn’t do what it’s supposed to.
Fortunately, there’s an extension for this. It’s called Sync On Arrival. So far, it’s working like a charm. The only thing I had to do was edit the install.rdf to increase the version number. It’s compatible with Thunderbird 2, even though it says it’s not.
Edit: see the comments for a way to do this with configuration alone, rather than an extension.