123, X Street, Y Avenue
[Subject: Normally bold, summarizes the intention of the letter] -Optional-
Dear Austin Parker,
As requested via email, we will be sending you 1 box of expandable envelopes. These envelopes are of smooth finish and with high durability. Also enclosed is a list of other colors available and also a cut out piece of our other envelopes with different textures. In case you might want to try the other kinds, you can just contact me per email, or call us at 2345678. Thank you.