Panasonic KX-PS8000 Operating Instructions Manual page 153

Envelopes
It is recommended that you print in black text only and purchase high quality #10 or
larger laser envelopes with diagonal seams, as shown in the diagram below:
High quality envelopes have the following characteristics:
BA thin, sharply creased leading edge
BPaper weight of 90 g/m
BFlat, free of curls, wrinkles, nicks, etc.
It is not recommended that you use envelopes with any of the following
characteristics (using these may result in paper jams):
BIrregularly shaped envelopes
BEnvelopes with curls, wrinkles, nicks, twists, dog-ears or other damage
BEnvelopes with side seam construction
BHighly textured envelopes, or with extremely shiny surfaces
BEnvelopes that seal by removing a peel-off strip
BEnvelopes with more than one flap to be sealed
BSelf-adhesive envelopes
BEnvelopes that are baggy or not sharply creased
BEmbossed envelopes
BEnvelopes that have previously been printed on
Side seam construction
Twist
Wave
2 (24 lbs.)
Peel-off strip
Curl
Dog-ears
Appendix
Multiple flaps
Bent-edge
Self adhesive
153