Mail file contains data but msf file is inconsistent
Facing sometimes conflicts on mail files, with a result that the mail file is "corrupted" and replaced by a file with a subset of the original one.
When trying to restore the older version of a mail file (containing all the data i.e. all emails), the msf does not rebuild correctly, bringing up the real content of that mail file. Repair folder does not help either.
Wšykne wótegrona (1)
If your account is IMAP then the file will synchronize to the set on the server. That sounds to me like what is happening.