This article discusses the implications for health research of Canada Post's transition from door-to-door postal delivery to community mailboxes. We argue that using postal code data to geocode participants based on community mailboxes will result in positional and linkage errors. Positional errors involve misplacing people's residential location. Linkage errors result from incorrectly linking residential location from community mailboxes to census or health administrative data. The article discusses examples of how the transition to community mailboxes could have important implications for health research. We encourage research examining the extent of positional and linkage errors on the 11 pilot communities transitioning to community mailboxes in the fall of 2014.