Epson 740 Series - Manual (Page 88)

Printing on Special Media Page 88
Envelopes
You can load up to 10 envelopes flap edge first, with the printable
side up, as shown below:
Select Plain paper as the Media Type and choose the correct
envelope size as the Paper Size setting in the printer software.
If ink smears when you print on envelopes or other thick media, set
the paper thickness lever to the + position as shown below. (Return
the lever to the 0 position before printing on other media.)
Note:
If the stack of
envelopes is more
than 0.4-inch
(10 mm) thick, press
the envelope edges
to flatten them before
stacking or load one
envelope at a time.