Brother HL-6050DN - Manual (Page 31)

1 - 23 ABOUT THIS PRINTER
Printing on envelopes from the MP tray
When the back output tray is pulled down, the printer has a straight paper path from the MP tray through
to the back of the printer. Use this paper feed and output method when you want to print envelopes.
1
Select the Paper Size, Media Type, Paper Source, and other settings in the printer driver.
Media Type: Envelopes
Paper Source: MP Tray
PCL (standard) printer driver
BR-Script printer driver
The printer automatically turns on the MP Tray mode when you put paper in the MP tray.