Dell 1250c Color Laser Printer - Manual (Page 66)

64 Loading Print Media
Loading Envelopes
NOTE: When you print on envelopes, be sure to specify the envelope setting on the
printer driver. If not specified, the print image will be rotated 180 degrees.
When Loading Envelope#10, DL, or Monarch
Load envelopes with the side to be printed on facing up, the flap side facing
down, and the flap turned to the right.
To prevent DL and Monarch from being wrinkled, they are recommended to
be loaded with the print-side facing up, flap opened, and facing you.
When Loading C5
Load envelopes with the side to be printed on facing up, with the flap open.