As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED TO DEPARTURE. AIRCRAFT WAS GROUNDED. FLIGHT CREW REPORTED THE OCCURRANCE OF AN LEFT AFT CABIN DOOR ECAM MESSAGE DURING INITIAL CLIMB OUT. THE CREW DECLARED AN EMERGENCY AND RETURNED TO BOS WHERE THE AIRCRAFT LANDED SAFELY WITH NO FURTHER INCIDENT. MAINTENANCE REPLACED PROXIMITY SWITCHES (PN DHE1141) 15WV1 AND 17WV1 ON THE LEFT HAND AFT CABIN DOOR PER AMM 52-71-11-401. A SATISFACTORY OPERATIONAL CHECK WAS ACCOMPLISHED.