AC does have a mailing list function.

However, I like to keep my mailing lists in an Access Database, with exports from AC. It contains historic patients from my other practice locations, check marks about who do not wish to receive mailings (as well as dismissed patients), consolidates families into "Family of" or sends to "Parent of". And finally, if you have a large practice and intend to bulk mail, you can scrub the AC, and therefore human entered, addresses with a third party.