Commercial envelopes – used for business correspondence, made from bond and craft papers in all standard sizes
Window envelopes – used primarily for statements, dividends, and invoices
Self-sealing envelopes – have latex adhesive on upper and lower flaps that seal instantly without moisture when the flaps come together
Booklet/Open-side envelopes – ideal for direct mail, with a concealed seam
Baronial envelopes – a more formal open-side envelope with a deep, pointed flap often used for invitations and greeting cards
Banker’s flap and wallet flap envelope – usually used for bulkier correspondence
Clasp and string-and-button envelopes – sturdy and are widely used for mailing sizable correspondence
Open-end envelopes – used for mailing catalogs, reports, booklets, and magazines
Expansion envelopes – used for bulky correspondence and packages