A drive apparatus for a mail-processing system is specified, which apparatus has an enclosure-collating path, which is intermittently driven at least in one end section, an adjoining inserting station for sets of enclosures and an envelope-filling table, which extends parallel to the enclosure-collating path and in front of the inserting station and over which envelopes pulled from a stack of envelopes are pulled by means of an envelope-gripper chain in front of the inserting station and held open there and, once filled with the sets of enclosures, are conveyed away by the gripper chain. A reduction of mass moments of inertia of the drive for the envelope-gripper chain together with simplification of the structure of this drive and a conveying system of a modular design are achieved by a drive section as a chain drive or toothed-belt drive being guided downwards from an intermittently rotating drive shaft out of the region of the enclosure-collating path to a chain wheel or a belt pulley which is mounted in a substructure of the envelope-filling table. From there, a chain drive or toothed-belt drive leads in the substructure of the envelope-filling table to a chain wheel or a toothed-belt pulley which is mounted at the free end of a rocker, the free end of the rocker undergoing an approximately vertically oriented guidance in the substructure of the installation, while the upper end of the rocker is supported and mounted coaxially in relation to a drive shaft for the envelope-gripper chain on the envelope-filling table which is displaceable in relation to the substructure. A chain drive transmits the intermittent drive movement finally from the lower end of the rocker to the upper end of the rocker, onto the drive shaft which is coaxial to the rocker pivoting axis and is intended for the driving-chain wheel of the envelope-gripper chain.