The description of bad format expansion

File format bad
File type:
The bad file is an e-mail message which could not be delivered to the recipient by Microsoft Exchange Server. The file includes the body of the message, the subject, recipient(s) and sender, quite similar to the original message content.
The file objects with bad extension are being stored in Badmail folder together with bdp and bdr files. If you need to view them, simply copy the files into the Pickup folder.