Address validation is the process of checking a mailing address against an authoritative database to see if the address is valid. If the address in question matches an address in the official database, the address “validates”, meaning it’s a real address. Addresses that do not match any addresses in the database are marked as “invalid”, meaning the address either doesn’t exist or isn’t registered with the official postal service. Most countries around the world have their own respective databases against which addresses can be validated.