I don't know about BackupApp (haven't heard of it) but I guess you can always use the old trick of "inserting" something (in this case the msg database file) on a backup (let's say, the first made backup for your "new" device on iTunes) and it should probably work, not even a jailbreak required.
You need to use a pretty expensive windows app tho (to sniff and mess with the backup), never tried it myself.