A mail processing machine which includes a folder bar, a creasing element and pressing roller assembly for maintaining an array of sheets in a folded over form in a reduced height stack for insertion into mailing envelopes. A table supports the lower surface of sheets to be processed by the machine, pusher bars engage and intermittently advance the sheets downstream of said machine. The folder bar extends transversely of the downstream direction and is arcuately movable to impart a fold to the array of sheets. A creasing element moves up to engage the lower surface of the stack, and two opposed pressing rollers, each with its own drive mechanism, are resiliently urged together to apply a pressing force to the array of sheets passing between the rollers.