Frustrated With Envelope Paper Jams!!

I own two HP all-in-one printers (5610 and 6000 series), and have significant problems printing #10 and 6″ x 9″ envelopes for our business. The 5610 is in our vacation home, and doesn’t have a lot of use on it – but jams envelopes 9 out of 10 times.

It is important to note that we only feed one envelope at a time (we don’t stack two or more envelopes in the tray).

I would love to hear from people who print envelopes on a regular basis – what printer make and model are you using? Any suggestions or advice would be greatly appreciated!