If you accidentally delete the attributes on your email files (by using tar rather than zip, for example, or by copying them to a non-BFS file system), you’ll find that it’s no longer possible to do queries on your email, or to enjoy the drag-and-drop access to attachments that BeOS provides. It also becomes very difficult to find a specific email message without opening up all messages, as the default naming scheme for mail messages on BeOS isn’t very descriptive. [Editor’s note: that’s what grep is for. 🙂 ]
However, there is a solution. You can pass the messages through BeOS‘ mail parser and it will recover all of the attributes, including the ones that allow you to drag-and-drop attachments. I recovered about a hundred otherwise-munged email messages this way.
Just launch a Terminal, navigate to the directory containing the messages, and type:

mail_parser *

Two caveats: first, the mail_parser opens up the newly-parsed message when it is finished, so if you have BeMail as your default mail program, hundreds of messages to parse mean hundreds of BeMail windows; and second, the mail_parser may mark directories with ‚New‘ status attributes, which will cause the Deskbar’s mail Replicant to report the presence of unread mail even when all of your mail is read. To fix this, you’ll need to delete the unwanted attribute from the command line, with the rmattr command.