HP LaserJet 8000 Multifunction Printer series - Manual (Page 269)

Appendix A Specifications 269
Paper Specifications
Envelopes with Double-Side-Seams
Double-side-seam construction has vertical seams at both ends of the
envelope rather than diagonal seams. This style may be more likely to wrinkle.
Be sure the seam extends all the way to the corner of the envelope as
illustrated below.
Envelopes with Adhesive Strips or Flaps
Envelopes with a peel-off adhesive strip or with more than one flap that folds
over to seal must use adhesives compatible with the heat and pressure in the
printer. The extra flaps and strips might cause wrinkling, creasing, or jams.
Acceptable
Unacceptable