So that's how I came to be using thunderbird. It took a while to get 3.1 installed (only 3.05 is in the repositories right now) and there's no 64bit .deb. Somehow I found a tar.bz2 for the 64 bit version, but for the life of me I cannot remember where. And the weirdest thing was was that it was just the directory that needed to be directly copied into wherever you wanted (no compiling, weird). So I copied that into lib or whatever, and then created a start menu item. So now it is installed, and is 64 bit!
I installed the lightning extension (there was a link when I opened mozilla in the what's new tab and that worked fine, thankfully) and a couple of other extensions and all was tops until I opened it this morning and got "unable to open the summary file for inbox thunderbird" etc. The internets told me to just delete the inbox.msf files where ever they are stored, but that didn't work. What I had to do was delete all my mailboxes, delete all the folders containing the msf files and do them all again.
But it doesn't stop there! Then I got these crazy errors when I attempted to delete items "The current command did not succeed. The mail server responded: [TRYCREATE] The requested item could not be found." on my IMAP account. Turns out it attempts to move it to a "Trash" Folder which does not exist on some IMAP accounts. So a manual workaround is here: http://kb.mozillazine.org/IMAP_Trash_folder
And guess what! It actually worked.
But of course I still can't get LDAP to work.