Adhere to the following guidelines to help ensure proper printing on envelopes and to help prevent printer jams:
Do not load more than 10 envelopes into Tray 1.
The weight rating of envelopes should not exceed 90 g/m2 (24 lb bond).
Envelopes should be flat.
Do not use envelopes with windows or clasps.
Envelopes must not be wrinkled, nicked, or otherwise damaged.
Envelopes with peel-off adhesive strips must use adhesives that can withstand the heat and pressures of the printer’s fusing process.
Envelopes should be loaded face-down with the top of the envelope to the left, and the short edge feeding into the printer first.
In high humidity environments, envelopes should be printed long-edge first to prevent them from sealing during printing. For long-edge printing, envelopes should be loaded long edge first, face down. See Printing envelopes from Tray 1 to change the printer driver’s envelope orientation.
HP 3550 3700 Envelopes