Print quality issues; Missing print/characters; Void lines; Blank/Void spots; Toner not fusing to envelopes
This problem may be due to the Envelope Enhance feature, which is built into the printer to help keep envelopes from wrinkling.
First try to eliminate the fuser unit as the cause:
Run some plain paper print jobs. If the print quality problem (missing print/characters) does not arise, you need to consider the weight and/or texture of the envelopes themselves. We recommend that you use regular plain paper envelopes in this printer. Try to avoid envelopes that are heavy or have a rough or textured surface.
There is an envelope weight setting you can adjust that may help with this problem. Do the following:
Go into the main printer menu, select PAPER MENU and then Paper Weight.
Change the envelope weight setting to Heavy. This will increase the fuser temperature for printing on envelopes and will help to melt the toner onto the envelopes correctly.
If none of the above tips helps to resolve the issue, there is a slight possibility that there is something wrong with the solenoid on the fuser unit, though this is unlikely as it would cause your envelopes to jam as well.