Epson Stylus 1500 Reference Manual page 29

Follow these steps to load envelopes:
1. Make sure you set the thickness adjustment lever to the
correct position for envelope printing, as described on
page 1-3.
2. You can load up to 10 envelopes in the sheet feeder with the
printable side facing down as shown.
3. Adjust the left edge guide so the envelopes feed straight
into the paper path.
4. If you are printing on oversize envelopes, remove the rear
edge guide and reinstall it to match the length of the
envelope, as shown above.
1-16
Paper Handling