Just what is a CMRA? Why is knowing this important?
A Commercial Mailing Receiving Agency (CMRA) is a private company that provides mailbox rental services to individuals and companies such as The UPS Store (formally Mailboxes Etc.) or FedEx Kinkos.
Being able to properly identify CMRA-based customers has many advantages, including fraud prevention, e.g. additional screening for CMRA-based customers. In other words, if you need to know where somebody lives, a CMRA box won't help you. If you know that you have the address of a CMRA mailbox, you can request the information you need and make other inferences.
More information at the official USPS site.
Any address processed using our LiveAddress service is closely inspected. If it is found to correspond to a CMRA it is flagged so that you can handle the address according to the needs of your business. See field definitions for details.