I'd like to start by saying that Firebird is my primary web browser, and I'm not a fan of Microsoft products, so it took a great deal of frustration with Thunderbird to get me to leave it entirely, but I have.
Thunderbird has two critical flaws that render it more trouble than it's worth. These are show stopper bugs for me, and I have no intention of touching Thunderbird again until they are addressed.
The first one, the one that I was going to try and ignore, had to do with upgrading from one version to another. Thunderbird would always lose my settings, and I'd have to go through a couple of hours of hoop jumping to get it to see the folders for my three work mail accounts. It was not fun, and I really didn't appreciate the fact that I had to go through all the convoluted "Migrate your settings" steps to get my messages back just because I upgraded from 0.7 to 0.8.
The second bug, the one that's wasted half a work day and a chunk of last night had to do with Compacting Folders.
Thunderbird uses the mbox format for storing it's data, and when you "delete" a message, it's not actually deleted from the text file that stores the data for that folder, it just marks the message as "deleted." Specifically, it sets "X-Mozilla-Status" to "0019".
Most mail clients do this.
What most other clients have, however, is a functional "Compact Folder" feature that can generally be configured.
What compacting a folder does is remove all of the messages that are flagged as "deleted" so the only messages actually in the folder are the ones that are NOT deleted.
Thunderbird 0.8 does not actually compact it's folders. It has menu options that claim to do it, and you can set thresholds at which Thunderbird will supposedly compact folders, but none of them actually cause Thunderbird to DO anything.
The end result, is I have a 1.5 GIG Thunderbird Mail folder.
One fun example is the Inbox on my primary account. Right now, there are NO messages in the inbox. It's empty, there's nothing there.
The inbox file is 169 MEGS.
I open the file up in VI, and what do I see? Every message I've ever received in that account recorded with the line "X-Mozilla-Status: 0019"
They're all "deleted" but they're still all there.
SO I did the natural thing. I right clicked on the folder and selected "Compact This Folder" and let it run.
Sometimes the throbber goes for five minutes. Last night was a couple hours. No matter how long I let it run, or how long it takes to build a "Summary file for Inbox" the file size does not change.
There were TWO messages in it, and lo and behold, it took Thunderbird FIVE MINUTES after launch to show them. It reports a blank mailbox until it finishes parsing the 169 MEG inbox.
I spent a good deal of time combing Google and Google Groups for answers. I even installed an extension that claimed to add a button for compacting folders, but no luck.
So I'm done. The bloated files have made the program slow and unmanageable. The hard drive is trashing needlessly, and I have massive files eating up my laptop's precious hard drive space to store messages that I deleted.
Emptying the trash does nothing.
File->Compact Folders does nothing.
I don't want to hear I should use a third party utility to compact the folders. It's a rudimentary function of a mail client, and if I have to install a third party program to do it, then the mail client is clearly note being coded properly.
So I'm done with Thunderbird. I might take another look when it hits 1.0, but if my tests show it still can't compact folders successfully, then I'll have to stick with Outlook.