I have an hp j3680 - I have tried all HP support suggestions. 81/2 X 11 paper prints just fine. Envelopes are pulled partially by the rollers, then they get stuck part way and I either get an "out of paper" or "paper jam" error message. I have tried stacking several envelopes and a single envelope in the envelope slot, but the problem keeps recurring.

SOURCE: envelope printing

I have an older, but similar, 5510 model with the same problem. A partial solution that works about 75% of the time is to tuck the envelope flap inside the envelope and give the end of the envelope that is to feed into the machine a slight curve by gentlly bending it on both sides. Then make sure there are only a few sheets of paper in the paper tray (less than 1/8" thick stack). Position the envelope so it is only about 1/2" from the end of the paper in the tray so the feed rollers have to transport it into the machine. I also have to set the margin for the return address in Word to be 1" from the edge of the paper so it prints in proper position, but this may be a problem with my Word 2000.