second johntheventer, we run thousands on our Xerox 700 machines. All flaps need to be open, we have never had a problem with wrinkling if you run as described above. We've never gone to the lengths of placing a card in the envelope to avoid the embossing effect although it does happen but has never been an issue with our customers, they like the quick turn and quality print. For window envelopes you need to purchase the "laser-safe" option which are more money but standard windows will shrink in the heat and curl the envelope. I've only run these through the bypass of the machine as a 5.8x9.5" size (LEF) and make sure you have "face-up" set or they'll jam in the inverter every time. Your envelope needs to be really close to those dimensions since that's the minimum length (5.8") the machine will run. Shorter flaps will not work, nor will #9's and smaller. Generally we only run #10's this way. For 9x12's we leave the flap closed and run LEF but do get creasing on these. We have had problems with skewing, our only solution to this has been to put less in the tray and it seems to help quite a bit. I usually max out at about 25 envelopes per lift in the tray but if I'm having skewing problems I usually cut that back to 10. It takes longer and requires the operator to stand right by the machine, opening flaps and loading but for 500 full color envelopes it's much faster than moving it to a press and we can use our current equipment rather than purchase a dedicated envelope printer. Make sure to use a junk fuser since the additional paper thickness really leaves a gloss differential line on the edge of where the envelope travels. Good luck.