Lexmark All in One Printer - Manual (Page 65)

65 Loading Print Materials
7 Load the stack of envelopes with the address side up and flap
side down. The flap side edge of the envelope should be
facing the left side of the envelope feeder. Make sure the
envelopes at the bottom of the stack slide into the envelope
feeder slightly more than the ones at the top of the stack.
N OTE : Do not try to load more envelopes by forcing
them under the envelope feeder weight. This
results in jams.
N OTE : Do not feed stamped envelopes.
W ARNING : Never use envelopes with clasps, snaps, windows,
coated linings, or self-stick adhesives. These
envelopes may severely damage the printer. See
“Envelope guidelines” on page 33 for more
information.