A flap separating mechanism for distending a flap from a body portion of an envelope.An envelope moving through a mail handling system may require its flap to be moistened and sealed. As a prelude to the moistening procedure, the flap of the envelope must be separated from the body portion. The separating mechanism disclosed herein comprises a rotatably affixed belt conveyor and an adjacent ski-like stripper member. The stripper member is movably biased toward said conveyor to provide a normal force on envelopes disposed therebetween.The deflapping mechanism can accommodate envelopes of varying thickness, while providing a fixed plane for the printing of postage on the body portion of the envelopes.