The mailing addresses in our database are guaranteed to be 97% deliverable. We clean up addresses against a certified CASS system, and also check our data against the postal service's NCOA system. We also process mail returns regularly, ensuring our database is as up-to-date as possible.
Doing all these things maximizes the chance that your mailings will get into a physician's hand, even if they've moved. It also helps lower your postage costs.