The sender's name and address go on the upper-left corner of the envelope. This section is called the "return address," as it provides the post office with a place to return the letter if the delivery cannot be completed due to insufficient postage or a problem with the destination.
The first line in the upper left is for the sender's full name. The second line contains the street address. The next line contains the city, state and ZIP code. Write "USA" under the address line when sending an international letter. The return address should be printed or typed for legibility.