The invention relates to a feeder device (1) for feeding mailpieces (2) to a postal sorting conveyor (3), the feeder device comprising an unstacker head (4) designed to put the mailpieces in series and on edge on the sorting conveyor, an unstacker plate (5) designed to unstack the mailpieces one-by-one towards the unstacker head, and a mailpiece feed conveyor (6) designed to convey the mailpieces in a stack and on edge against the unstacker plate. The unstacker plate comprises a stationary portion (5a) that extends from the unstacker head, and a moving portion (5b) that extends the stationary portion, said moving portion being mounted to pivot from the stationary portion between a first position in which the stationary portion and the moving portion are aligned with each other, and a second position in which the stationary portion and the moving portion are angularly offset relative to each other.