Place the stack of mail on the feed deck. Place the envelopes with the flap side facing down and the top edge against the rear wall.
Slide the side guide up to the mail stack. Leave about 1/8" space (about the thickness of 2 quarters) between the stack and the side guide to ensure the stack feeds without resistance. Leave about 3 mm space between the stack and the side guide to ensure the stack feeds without resistance.
Slide the stack into the feeder until you feel resistance. Note the side guide has been pulled back in the image to show how far into the feeder you need to position the stack.
UPDATED: November 03, 2020