Answer: pilesup

AnswerCrossword Clue
PILESUPAccumulates
PILESUPAmasses
PILESUPSaves
PILESUPMore than fills the inbox
PILESUPAccumulates.
PILESUPAmasses.
PILESUPGrows
PILESUPAmasses, as debt
PILESUPMakes a stack