Abstract: In an envelope-filling apparatus for mail-processing machines, the adjustment of the push-in depth of enclosures into open envelopes in the operating stroke of a pivot-lever arrangement, which bears a push-in-finger arrangement, is simplified in that said pivot-lever arrangement is designed as a three-lever rectilinear-guidance mechanism, of which the third lever, which serves as the carrier hand for the push-in-finger arrangement, has, at its free end, a slide guide which can be secured and is intended for adjusting the distance between a push-in-finger shaft for the push-in-finger arrangement and the point of articulation of the longer lever of the three-lever rectilinear-guidance means on the carrier hand.