Sending a piece of mail sounds simple, but mailing to a post office box actually involves a few challenges. Among the considerations, as noted by Terry Babcock, Distribution Clerk for the Estes Park, Colorado post office, you need to know what prevents the mail from arriving at the intended destination: "High speed sorting machines not only provide certain advantages in getting mail delivered, but also certain requirements to ensure the mail isn't returned to sender."
Get the correct post office box number. United States Post Office personnel do not have the authority to give out personal P.O. box numbers, but they can help you find the box numbers for businesses. An online source of P.O. box numbers for businesses is namesandnumbers.com. The company also produces printed versions of the information, which includes P.O. boxes for individuals in the service area.
Provide a ZIP code. The first three digits of the ZIP code refer to a sorting facility, so the three-digit number for Estes Park, Colorado, for example, is "805." After that the sorting machines, which even have the ability to read cursive writing, scan the numbers to direct the mail to specific locations.
Use the full, nine-digit ZIP code whenever possible. Keep these examples in mind to show the value of using the nine-digit ZIP code. (1) A P.O. box for the American Express payment center in Dallas, Texas is 650448; the nine-digit ZIP code is 75265-0448. The last two digits of the first part of the ZIP code and the four final digits are the numbers of the P.O. box. (2) A P.O. box for a resident in Cornwall, Pennsylvania is 135; the nine-digit ZIP code is 17016-0135. In each case, the U.S.P.S. can route the mail more easily if the nine-digit zip code is used -- despite the obvious correlation to the P.O. box -- simply because of the way the sorting machine scans the address.
Ask for the mailing address when mailing anything to a business. Do not assume that the physical address on a business card or letterhead is the mailing address. Some jurisdictions require a P.O. box for mail delivery, although the business may choose not to list the P.O. box number on collateral. If you mail anything to that business using only the non-P.O. box address, the U.S.P.S. has no obligation to deliver it.
Call the recipient when in doubt on delivery of a P.O. box package mailing. The delivery confirmation options available through U.S.P.S. do not guarantee that the P.O. box holder has received a package. When the package arrives, a notice of receipt goes into the appropriate P.O. box, but prior to that, post office personnel have scanned the delivery-confirmation notice to indicate receipt. That means that the sender might have assurance from the U.S.P.S. that the package arrived, but in fact, the intended recipient hasn't picked it up. To ensure that the letter or package actually reached the intended recipient, make a phone call.