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.