Canon Color Bubble Jet BJC-1000 Series User Manual page 41

The following envelopes are not recommended because they may cause
jams or smears, or may damage your printer.
Envelopes with windows, holes, perforations, cutouts, and
double flaps.
Envelopes made with special coated paper or deeply
embossed paper.
Envelopes using peel-off sealing strips.
Envelopes in which letters have been enclosed.
When you are ready to print on envelopes, follow these steps to stack
envelopes in the sheet feeder. (You can also manually feed envelopes one
at a time.)
Prepare the
printer.
3-12 Paper Handling
Open the front cover and make sure that the blue paper
thickness lever is set to the right (A).
Close the front cover.
PAPER THICKNESS LEVER
Chapter 3