Epson LQ-1050X User Manual page 82

CAUTION: Envelope printing is available only at normal
temperature (41°F to 95°F or 5°C to 35°C).
To make sure that the printing fits within the printable area, always
print a test sample using a normal sheet of paper before printing on
envelopes.
Paper Handling
2-34
0.33 inch
(8.5 mm) or more
0.87 inch
(22 mm) or more