Hi lavie, welcome to the crash-fest 🙂
Unless you have a bad preferences file, it looks like one of your mailboxes has a corrupt table of contents, and fixing that in Mac OS X 10.3.x isn't going to be an easy task. Start by verifying/reparing your filesystem as described here:
The Repair functions of Disk Utility: what's it all about?.
If Mail still crashes, try this first:
1. Make sure Mail is not running.
2. Make a backup copy of the
HOME/Library/Mail folder, just in case something goes wrong. You can do this in the Finder by dragging the folder to the Desktop while holding the Option (Alt) key down, for example. This is where all your mail is stored.
3. In the Finder, go to
HOME/Library/Preferences/. Locate the file
com.apple.mail.plist and move it to the Desktop (to be deleted after fixing the problem).
You'll have to set up your accounts from scratch all over again. If given the option to import existing mailboxes or something like that,
don't. Just enter the account information and Mail will automagically rediscover the data in
HOME/Library/Mail/ when done.
You'll also have to re-configure most of your settings in
Mail > Preferences. The first thing you should do is go to
Preferences > Viewing and disable "Display remote images in HTML messages" if it's enabled.
If mail still crashes after recreating the preferences file, it means that was not the problem, so you may want to move the
com.apple.mail.plist back to where it was.
Also, if Mail keeps crashing, please start a new thread describing more accurately under what circumstances Mail crashes in order to be able to identify the mailbox that has the problem. It may end up being a long thread and it has nothing to do with the OP's problem, so I'd rather discuss it separately from this one.