Panasonic KX-FLB881 Operating Instructions Manual page 28

3. Printer
Waved Dog-eared
Do not attempt to print on any of the following types
of envelopes (these may cause damage to the unit):
L Envelopes with clasps, snaps or tie strings
L Envelopes with transparent windows
L Envelopes that use encapsulated types of adhesive
that do not require moistening but rely on pressure to
seal them
Clasp
28
Self adhesive
Transparent window