E-mail message that could not be delivered by Microsoft Exchange Server; includes the message sender, message recipient(s), subject, and body, just like the original message. BAD files are stored in the Badmail folder along with .BDR and .BDP files; they can be viewed by transferring them to the Pickup folder.
The BAD file extension is associated with the Brutus. The .bad files contain configuration information for Brutus, usually for a particular authentication type/device. Brutus can import and export *.bad files so you can install new authentication types (applications) into Brutus or you can create new custom authentication types and export them for others to use.