Brother MFC-8420 User Manual page 182

4
Using both hands put the envelope in the manual feed tray until
the front edge of the envelope touches the paper feed roller and
the MFC will grip the envelope.
Make sure the envelope is straight as you insert it in the
manual feed tray. If it is not, the envelope may not be fed
properly, resulting in a skewed printout or a jam.
Do not put more than one envelope in the manual feed tray
at any one time, or it may cause a jam.
Put the envelope in the manual feed tray, making sure that
the side to be printed on is face up in the tray.
5
After the printed envelope comes out of the MFC, the MFC will
wait until you put in the next envelope. Repeat Step 4 for each
envelope you want to print.
6
Send the print data to the MFC.
7
After you finish the print job, close the back output tray.
USING THE MFC AS A PRINTER 11 - 14