Epson Stylus Color 980 Daily Use page 17

Load envelopes flap edge first with the flap side down, as
shown in the illustration.
Do not use envelopes that are curled or folded. Flatten the
envelope flaps before loading. Avoid using envelopes that are
too thin as they may curl during printing.
Select Plain Paper as the Media Type setting in the printer
driver.
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Available envelopes sizes are:
No.10, DL, C6, 132 mm 220 mm