Canon MX720 Series Online Manual page 63

(5) Slide the paper guide
sides of the envelopes.
Do not slide the paper guides too hard against the envelopes. The envelopes may not be fed
properly.
Note
Do not load envelopes higher than the load limit mark (F).
Keep the envelope stack height below the protrusions
(6) Insert the cassette (lower) into the machine.
Push the cassette (lower) into the machine until it stops.
3. Open the paper output tray.
(1) Holding both sides of the paper output tray, gently open it.
The output tray extension opens automatically when the paper output tray is opened.
(2) Extend the paper output support.
(B) on the right to align the right and left guides with both
(G) of the paper guides.