Epson STYLUS SCAN 2500 Manual page 56

Load envelopes flap edge first with the flap side down, as shown
in the illustration.
❏ Do not use envelopes that are curled or folded. Make sure to
flatten the envelope flaps before loading. Also avoid using
envelopes that are too thin as they may curl during printing.
❏ Select Plain Paper as the Media Type setting on the printer
driver.
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Available envelopes
sizes are:
No.10, DL, C6