This sounds like an issue with your printer. I'm no authority on printers, but the three I routinely use allow envelopes to be inserted either way, which is sometimes a pain because it's so easy to load them the wrong way.
If it's not a printer issue, Filemaker allows you to rotate objects in ninety degree increments.
Well, as I said, the printer does fine with envelopes from other applications (like Microsoft word), and it USED to work with Filemaker.
I should install an older version (if I can find the disc) and see what happens).
Yes, I already have made rotated views that get the results I want, but that seems far from perfect.