We have individually branded funds, which require unique letterhead and envelopes.  We have it set up to do the conditional merge for both letters and envelopes in "Mail --> Donor Acknowledgement Letters".  The issue is, you have to remember to NOT mark as acknowledged when you run the letters, and then MARK them as acknowledged after you run the envelopes.  Creates many challenges if you forget either step.

It would be WONDERFUL if the the "Mail --> Envelopes" section would allow us to do conditional merge and edit envelope so we could add in branding and return address based upon the condition like it is set up in letters.  

THEN, we could use the "create gift output query", mark the letters as acknowledged, run the envelopes using the saved output query and wouldn't have to worry about whether we did or didn't acknowledge the letters.  Life would be grand!