What was found
CLT FLT 985 EN ROUTE CLT TO MBJ. AFTER PUSHBACK FROM THE GATE, WITH THE PARKING BRAKE SET, ENGINE TWO RUNNING AND NUMBER ONE ENGINE START COMMENCING, THE CABIN CREW REPORTED FUMES IN THE CABIN. THE FLIGHT RETURNED TO THE GATE. ODOR DUPLICATED WITH ENGINES RUNNING & ACFT POSITIONED WITH A TAIL WIND. FOUND AFT SERVICE DOOR COSMETIC SEAL MISSING A SECTION. REPLACED MISSING SECTION OF SEAL. PER ENGINEERING, REPLACED RECIRC FILTERS WITH POST MOD FILTERS. TEST FLIGHT SATISFACTORY.