In rare cases archives from Mail Archiver can become corrupt. Light cases of corruption can be fixed by cloning the archive. In bad cases the emails have to be exported to mbox. Because the corrupted location is not known before exporting I have to work around the corrupted location.
I have made a test archive and removed some bytes with a hex editor to make the archive corrupt:
The easiest way to locate the corruption and not have too much work is to export the emails account by account. So I select my GMX account and click on Export -> Current Mailbox and Sub-Mailboxes:
Then I get the export window:
I have a folder where I can export my emails to. The folder needs to be on a hard disk with lots of free space! I want to use eml files so that I get one file for each email. As I have archived from Mail I can't use MBOX files with minimal fields. With this option I wouldn't get the attachments from Mail.
The account only has one email, but the account itself is okay:
Onwards to the next account which I export now:
Since I only have the 2 accounts in the archive the corruption must be here. A real error message would likely show something about a corrupted segment map:
And the export stops before finishing:
In the mailboxes of the exported emails I can see that the problematic mailbox is "ganz viel viel text..." because there is only one email:
I can now export the other submailboxes of the Mothsoftware-Test account. Then I can try to narrow down the corrupted emails in the mailbox with the long name. Rinse and repeat if the archive has other accounts.
The resulting eml files can be imported into a fresh archive.
This is not a fun task!