An envelope processing apparatus for enclosing an enclosure in an envelope includes an envelope conveyance path, an enclosure supplier, an envelope supplier, a flap opener, and an envelope stacker. The envelope conveyance path extends in a substantially vertical direction to convey the envelope. The enclosure supplier supplies the enclosure to the envelope via the envelope conveyance path. The envelope supplier supplies the envelope to the envelope conveyance path, The flap opener opens a flap portion of the envelope between the envelope supplier and the envelope conveyance path. The envelope stacker stacks the envelope ejected from the envelope conveyance path.

An envelope sealing and flipping system can be incorporated into a mail inserter system to seal an envelope with a complete unbroken glue line and simultaneously flip the envelope face-up for downstream processing. The system includes a flip cage that receives an envelope and a moveable wetting brush that contacts the flap. The flip cage rotates, causing the flap to drag underneath the wetting brush, and realigning the envelope with a sealer nip which seals the envelope. The flip cage rotates continuously to receive, flip, and seal many envelopes.