You can print on plain paper envelopes in this size:
No. 10 (4.1 × 9.5 inches [105 × 241 mm])
Open the paper support and pull up the extensions.
Open the output tray and pull out the extensions.
Slide the edge guide left.
Load up to 10 envelopes against the right side, printable side up, and flap edge left. Then, slide the edge guide against the envelopes, but not too tightly.
Always follow these envelope loading guidelines:
If you have trouble loading a stack of envelopes, press each envelope flat before loading it or load one envelope at a time.
Do not load envelopes that are curled, folded, or too thin.
Paper Loading Capacity