FAQ Which Bulk Mail presorts does MAILERS+4 support? MAILERS+4 supports Standard, Periodical and First-Class postcards, letter, cards and flats. Most mailing types can qualify for Enhanced Carrier Route Automation, Enhanced Carrier Route WS/HD/LOT, 5-Digit auto/non-auto , 3-Digit auto/non-auto, ADC auto/non-auto, or Mixed ADC auto/non-auto.