To send large envelopes, you do not need to visit the Post Office, as long as you have postage stamps, access to a postage meter, or can print postage online from a company like Stamps.com. Simply address your envelope, affix the correct amount of postage to the upper right corner, and drop it in a collection box or hand it to your mail carrier.

Put the recipient’s address in the center of the envelope and the return address in the top left corner. Be sure all your information is accurate and list it in the correct order to make your mail arrive safely at its destination. You’ll also want to follow the measurement requirements for large envelopes to pay the correct amount in postage.

If you want to send letter-sized papers without folding them, you can use a large envelope (called a "flat"); the postage for flats starts at $1.39. If your large envelope is nonrectangular, rigid (can't bend), or lumpy (not uniformly thick), you'll have to pay the package price.

The post office prefers large envelopes to be mailed using landscape orientation. The return address goes in the top left corner, just like it does on smaller envelopes. The delivery address should start at least 1 inch to the right and 1 inch below the return address.