The mailing addresses in our database are 97% deliverable. We use a certified CASS system to clean up addresses, in addition to checking our data against the United States Postal Service NCOA system. We also process mail returns regularly to ensure that our database is as up-to-date as possible.
Doing all of 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.