I send most USA and Canada QSL cards as postcards, but I like to send DX QSL cards in an envelope, with postage included.
I have received some QSL cards in envelopes, and those envelopes exactly fit the standard 3-1/2" x 5-1/2" Cards. However, I have been unable to locate a source for such envelopes. Even the printer who makes my QSL cards does not carry them.
Where can I obtain such envelopes? Thanks.