Lexmark XC9455
The trays automatically detect the size of plain paper. For specialty media like labels, card stock, or envelopes, do the following:
From the home screen, touch Settings > Paper > Tray Configuration > Paper Size/Type > select a paper source.
Set the size and type of the specialty media.
This article shows the primary information required to escalate media issues.
Follow these steps in loading the envelope tray for you to print envelopes in bulk.