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What is a Mail Stop?

David White
David White

Under the category of those things that most people simply accept even though they don't know why they're there is the mail stop. This is a four-digit code that shows up after a ZIP code in a US postal address. That four-digit code designates a specific part of a mail delivery area.

A city might have a few ZIP codes to divide it into mail delivery areas. Those mail delivery areas are usually further subdivided into smaller areas, each with a mail stop. For example, the ZIP code of 33004 might have four mail stops: 33004-0001, 33004-0002, 33004-0003, and 33004-0004.

A mail stop is the four-digit code following the ZIP code in a US address.
A mail stop is the four-digit code following the ZIP code in a US address.

A college or university might have its own ZIP code, especially if the institution is within a city's boundaries. In this case, each department might be given its own mail stop. If the college's ZIP code is 66124 and the mail stop of the chancellor's office is 0100, then the full ZIP code of the chancellor's office would be 66124-0100.

In the case of a college or university or a large business that has its own ZIP code, the mail stop is a physical place as well as a set of numbers. The mail that is to be delivered to the chancellor's office in the above example will be delivered to stop 0100. In some cases, this is just the office; in other cases, it is the central sorting facility for something like a large college department. In this case, the location is literally where the mail stops.

Mail stops are used by the post office to designate areas of mail delivery.
Mail stops are used by the post office to designate areas of mail delivery.

This literal designation of the mail stop refers to the inner workings of a post office as well. The ZIP code 33004-0002 is labeled 0002 within the 33004 section of the post office sorting facility, and all the mail designated to be delivered to 33004-0002 "stops" there. The postal service will certainly deliver mail that does not list the last four numbers. Like the ZIP code, however, they help mail delivery folks sort and deliver mail more quickly and efficiently. Failure to include the mail stop in a ZIP code could delay delivery of mail.

What Is a Mail Code?

Mail codes are often used by universities and large businesses to designate specific departments, customers or other subgroups to make mail sorting easier and more efficient. The mail code is usually an additional designation added to the ZIP+4 code used by the post office and can designate different things for different organizations.

How To Stop My Mail?

The United States Postal Service will hold your mail for up to 30 days if you request the service. You can request to have your mail held online, at your local post office or by phone. If you need your mail held longer than 30 days, you will need to sign up for a forwarding service. You can also edit, change or cancel your hold request online or at your local post office. Once the hold is over, you can get your mail at the post office or have it brought to you. You must do this within 10 days or the mail will be returned to the sender.

What Is United States Postal Service Tracking?

USPS tracking provides a way for customers and businesses to track where a domestic shipment is along its shipment route. You can also find out when it has been delivered, when it was sent and when it is expected to be delivered. You can track a package by entering the tracking number on the USPS website.

How Does USPS Tracking Work?

Postal employees or shipping partners scan the label on trackable items at various points along the route. Each time the label is scanned, the location of the package should be updated.

How Long Is Tracking Information Available?

Tracking records are stored for an amount of time that varies depending on the service. USPS Tracking Service data is stored for 120 days. Signature Confirmation Service is stored for one year. The rest of the services' data is stored for two years.

What Can I Do If My Mail Isn't Delivered?

First, check the USPS website for the delivery standard for the class of mail you are expecting. The post office does not consider mail late until a certain number of days after the date of mailing has passed. Five or more days after the mailing date is considered late for First-Class letters and packages and Priority Mail. USPS Retail Ground, Media Mail, Bound Printed Matter, Library Mail, Parcel Select, Periodicals and USPS Marketing Mail are not considered late until 14 or more days have passed from the date of mailing. Priority Mail Express is guaranteed, so it is late once the guaranteed date has been missed.

If your mailpiece has a tracking number, the tracking information may indicate what the delay is. If not, you can check with your local post office or contact customer service.

What If the Tracking Information Says My Package Was Delivered, but It Wasn't?

First, check all of the areas where the carrier may have left your package:

  • Mailbox
  • Garage
  • Porch
  • Exterior doors
  • Area protected from weather

Next, check your mailbox again. Sometimes packages are delivered at a different time than regular mail. Ask your household members if they have the package. Wait 24 hours. Sometimes a package may be scanned as delivered, but arrive up to 24 hours later. If 24 hours have passed and your package has not arrived, you can email a service request to your local post office.

What Happens If the Mail Carrier Can't Get to My Mailbox?

If the mail carrier can not get to your mailbox because of weather or an obstruction, such as utility work or a parked car, your mail will go back to your local post office and your carrier will attempt to deliver it again the next business day. If your mailbox will be inaccessible for an extended period, you can schedule a redelivery or pick up the item at your local post office.

What Are Service Standards?

Service standards are the number of days that USPS considers to be a timely delivery for various classes of mail. Service standards provide customers with an idea of how long to expect various types of mail to take to get from one location to another.

Why Did My Carrier Refuse To Deliver Because of a Dog on My Property?

Delivery employees may suspend delivery services if there is a safety hazard, such as a loose dog, on the property. You will be notified if your mail can not be delivered due to a safety issue. Dog owners are expected to confine their pets during delivery hours.

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Discussion Comments


And that the mail stop is the same as the PO Box number is very helpful when the post office requires you to have a PO box because you reside too close to make it worth their while to drive your mail to you. Too many times a shipper has required me to remove my PO Box because it isn't supported in their system, but then they send it via USPS anyway, and the folks at the PO flag it as an undeliverable address, give me a pink slip, call me back, tell me I need to put the PO on the address line 1, etc. At least including the 4-digit mail stop will help to make their life a little easier, anyway.


I can see how adding the mail stop number makes it much easier to sort and deliver mail. This would help at the sorting stations for the post office as well as the mail room at large organizations.

Years ago I worked in a mail room before they used the mail stop numbers. This would be a better way to make sure the mail gets to the right place the first time.

Receiving a piece of mail without a ZIP code wasn't that frustrating for me, but I can see how it would be for someone who worked at the post office. It would really slow things up if someone had to manually look up the correct ZIP code for a location.


If I have a mail stop number written down for easy access, I will use it, but I never go out of my way to find out what it is. Now that I understand how this helps mail be delivered more efficiently, I will probably make more of an effort to use it. I just figured it was something that pertained more to large places of business than it did for personal mail.


I never really knew why they added the mail stop number, and never even knew what it was called. I just remember when they added 4 extra digits to the end of your zip code. I am sure everyone has their ZIP code memorized, but I wonder how many people know what their mail stop number is?

I have no idea what my mail stop number is without looking at a piece of mail. When it comes to sending out personal mail, this is something I rarely use and just go with the traditional ZIP code.


@empanadas-- I have a P.O. Box and never realized the mail stop number on my mail was the same as my box number. I really never gave it much thought, but when you know the story behind it, you can see how it makes sense.


thank you very much for that article. --Cleeon


You will often find that a mail stop is the same as a P.O. Box number. For instance, if you're P.O. number is 5090, you will see your zip code like this: 75858-5090, which will indicated exactly which P.O. Box to drop it at on that mail stop.


Interesting information. Never knew what it exactly meant, or that the four digit actually had a name.

I actually thought that mail stop and mail hold could be used interchangeably.

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    • A mail stop is the four-digit code following the ZIP code in a US address.
      A mail stop is the four-digit code following the ZIP code in a US address.
    • Mail stops are used by the post office to designate areas of mail delivery.
      By: chrisdorney
      Mail stops are used by the post office to designate areas of mail delivery.