Postal stationery - envelopes
Many postal services released "official" envelopes, usually pre-stamped, with a logo to promote a specific event or cause. Not to be confused with First Day Covers, these envelopes are not tied to a specific stamp.
Please e-mail me with pictures and information of any additional pre-stamped and postally-released envelopes you have. Postal stationery in postcard form can be found on the postcard page.
There are so many postal stationery releases (over 150) that India has its own page.