A Post Office Box is a beneficial option for someone who is in the middle of moving from one location to another; someone who has concerns about the privacy of her home address; and for businesses. Mailing a letter to a P.O. Box is similar to mailing a letter to a physical address, with only minor differences in the address. There are also certain types of services that are not available to a P.O. Box.

Place your letter in the envelope and seal it. Affix your stamp to the upper right corner.

Write your return address in the top left corner, just as you would for any other letter.

Write the address you wish to mail the letter to in the center of the envelope. Begin with the name of the person or organization you are writing to. Below that, write the address. Begin with words "P.O. Box" and then the box number. Below that information, write the city, state and Zip code. Never write both the P.O Box and the street address. This will create confusion and your letter may not be delivered.