An apparatus for feeding envelopes, containing contents, from a stack, comprising: an input bin for receiving a stack of envelopes so that each envelope is in a generally vertical orientation; a feed station with a feeder for feeding envelopes from the stack of mail in the input bin and a discharge drive for receiving envelopes from the feeder and driving the envelopes to a cutting station, the feeder comprising a plurality of rotatable belts that are entrained by a drive pulley driven by a feeder motor and a driven pulley mounted on a feed arm pivotable about an axis of the drive pulley, pushing means for displacing the stack toward the feeder, said pushing means comprising a pusher and a plurality of belts and a guide in the form of a collar that rides along a guide rail; a feed sensor for sensing the pressure of the stack against the feeder, wherein the feed sensor is configured to detect the deflection of the feed arm or the force applied to the feed arm, being proportionate to the pressure of the stack against the feeder; the feeder motor for driving the feeder to attempt to feed a document from the stack; a feeder exit sensor for detecting whether the feeder fed the envelope from the stack wherein the feeder exit sensor is positioned downstream of the feeder and upstream of the discharge sensor, the feeder exit sensor being configured to detect the envelope as it leaves the feeder, a discharge sensor for detecting the envelope when it leaves the discharge drive; a drive mechanism for driving the pushing means, said drive mechanism being the plurality of drive belts and wherein said plurality of drive belts are located in the bottom of the input bin, characterized int that the drive mechanism is configured to iteratively drive the pushing means toward and away from the feeder to attempt to feed the envelope, wherein the drive mechanism operates in response to the sensed pressure of the stack against the feeder and the detection that the feeder has not fed the envelope from the stack. an input bin for receiving a stack of envelopes so that each envelope is in a generally vertical orientation; a feed station with a feeder for feeding envelopes from the stack of mail in the input bin and a discharge drive for receiving envelopes from the feeder and driving the envelopes to a cutting station, the feeder comprising a plurality of rotatable belts that are entrained by a drive pulley driven by a feeder motor and a driven pulley mounted on a feed arm pivotable about an axis of the drive pulley, pushing means for displacing the stack toward the feeder, said pushing means comprising a pusher and a plurality of belts and a guide in the form of a collar that rides along a guide rail; a feed sensor for sensing the pressure of the stack against the feeder, wherein the feed sensor is configured to detect the deflection of the feed arm or the force applied to the feed arm, being proportionate to the pressure of the stack against the feeder; the feeder motor for driving the feeder to attempt to feed a document from the stack; a feeder exit sensor for detecting whether the feeder fed the envelope from the stack wherein the feeder exit sensor is positioned downstream of the feeder and upstream of the discharge sensor, the feeder exit sensor being configured to detect the envelope as it leaves the feeder, a discharge sensor for detecting the envelope when it leaves the discharge drive; a drive mechanism for driving the pushing means, said drive mechanism being the plurality of drive belts and wherein said plurality of drive belts are located in the bottom of the input bin, characterized int that the drive mechanism is configured to iteratively drive the pushing means toward and away from the feeder to attempt to feed the envelope, wherein the drive mechanism operates in response to the sensed pressure of the stack against the feeder and the detection that the feeder has not fed the envelope from the stack.