Epson EPI-4000 User Manual page 113

To print an envelope, place it inside the paper feeder with the
envelope opening entering the printer first and the front of the
envelope facing up. Align its left edge against the envelope
guide inside the paper feeder, as shown below.
8. If you are loading a sheet of paper, move the right paper guide
so that it rests lightly against the right edge of the sheet, as
shown below.
Loading Paper
Paper Handling
3-19