Some users are experiencing a problem in which large emails get stuck in the "Drafts" mailbox and cannot be deleted. Attempts at removing the file cause Mail to crash, and the file remains in the folder.
As described by Apple Discussions poster Mariela:
"I can't delete an email that was way to big and is now stuck in the draft folder. I have tried to delete it but mail crashes. Tried to delete it in the library folder but can't find it."
The individual messages in the Mail folder in the Finder are named with a unique identifier code, so a content search of a message must be done to locate it. Since this problem appears to lie with Mail mishandling the problematic email message, there are several things users can try to access the message and remove it without having Mail render the message and potentially crash.
Temporarily turn off the preview pane It is possible that Mail crashes upon trying to display the problematic email when it is selected. To keep the message from displaying, close the message viewer by either dragging the separator bar to the bottom of the window or double-clicking the bar. If Mail will crash upon loading because it automatically displays the message, hold the shift key when starting the application to ensure no messages are selected at load.
Manually locate and remove the problematic message Manually searching for and deleting the problematic email in the Finder should also get rid of the problem. Open the ~/Library/Mail/ folder and locate the Drafts.mbox mailbox folder (or other location that contains the problematic email) somewhere in the Mail folder directory tree (The default location is in the "Mailboxes" folder, though it can be anywhere, depending on how users have customized their Mail folders).
Optionally users can perform a Finder search in the "Mail" folder for the problematic email. Open the "~/Library/Mail" folder in the Finder, and press command-F to search. Then select "Mail" (next to "This Mac") and then search by "Contents". Enter some search text to isolate the email and then move it to the trash.
Remove the mail preferences files It is possible these problems are due to corrupt preferences file for the Mail application, and removing this file might also work. To do this, go to the ~/Library/Preferences/ folder and remove the "com.apple.Mail.plist" file. Then restart the Mail application to create a new one. Email account information will need to be re-entered, but all messages and mailboxes should be as they previously were.
Reinstall Mail Use the application Pacifist to locate the Mail application on the Leopard DVD and reinstall it, which may provide default settings that will allow for proper handling of the problematic email messages.