Epson Pro 5000 Reference Manual page 63

Note:
Load envelpes flap side down with the flap edge against the left
edge guide. For C5 envelopes, load the flap edge (short edge) first
with the flap side down.
6. The printer feeds the sheet automatically, and the printer
starts printing when you send a print job from the
computer.
When the printer finishes printing, it ejects the sheet. If the
sheet does not eject completely, press the Eject button.
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Paper Handling
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