Does the U.S. Postal Service have a size requirement for the smallest a letter can be to mail it?

I am planning on sending funny valentines to my friends via USPS.

My valentines are are about 2 inches x 4 inches in size.

Can I mail these out in their little given envelopes or does the U.S. Postal Service only accept letter mail between a certain size requirement?



If you can, I would like to have a link supporting the source of your info, as I do want my letters to be delivered to their destination.



Thanks!Does the U.S. Postal Service have a size requirement for the smallest a letter can be to mail it?
That will be too small.Does the U.S. Postal Service have a size requirement for the smallest a letter can be to mail it?
You can mail anything you want through the postal service. If it is too small put an additional 20 cents postage on it for irregular size. It is a good shape though. If it were square you would need another 20 cents but you are good in that dept.Does the U.S. Postal Service have a size requirement for the smallest a letter can be to mail it?
You have to put it in a reguirement approved size and that is not one u can go to ups.com and see all reguirements good luck