If someone enters an invalid apartment number, will that be caught and explained in the data returned from the BatchLeads system? For instance: if a building has apartments with letters A-K, and someone enters in an address with "apt #5," will your system indicate that something is wrong?

First, a little background on how and when the USPS stores apartment information. Think of an apartment building like a business. You have the lobby and then you have additional internal addresses (the apartments). The building, with the lobby, doesn't change but the apartments will certainly change tenants, and even two apartments might remodel to combine to make one larger apartment. The USPS needs a way to handle these changes.

Because USPS's goal is to deliver mail as quickly as possible without errors, they keep a list of as many internal addresses as possible. However, it is up to the building owners to submit any changes to the internal addresses. For the most part, the USPS knows what apartments exist within an apartment building. They even keep track of which ones are vacant and when the vacancy status changes. The system works most of the time. However, it is not a perfect system, and there are many variables to consider. It is possible that building owners make changes without informing the USPS, which can then affect accurate mail delivery.