 used bears a little bit of discussion, as well. If the data that make up the body of a message are already present in the application's document, by all means pass the address to them and mark the body data as volatile (you may not be about to free them, but you also can't guarantee the Mailbox library that they'll be around when the message needs to be sent). If you need to perform any conversion, however, you should use the Mailbox library's utility routines to obtain an appropriate VM file. Then you don