When I was setting up a test account on Linux Mint, I had no issues with Thunderbird’s account wizard in Thunderbird 3.1. However, when I tried to setup the same account in Thunderbird 5 or 7 it seemed the latest ‘improvements’ to the account wizard broke the automatic setup. Specifically the point where it attempted to verify the domain’s MX Records to get the correct server settings.
I had posted about this in the Thunderbird Builds forum and was informed Bug 663971 had just been patched and to allow a couple days to hit both Miramar (Thunderbird 5) and Shredder (Thunderbird 7). Finally had a chance to check while I had Mint running yesterday and was able to get the accounts setup immediately.