On 2.5.2012, at 20.27, Daniel L. Miller wrote:

I have isolated the corruption in a mailbox to 4 mdbox files. Two of these (smaller) files cause the force-resync to report a breakage and save the file as m.XX.broken. The other two (larger) files cause a crash.

Is there a way I can fix these files and recover the mails?

Well, you do have the option of extracting the mails with a text editor until I get around to fixing the crash.