posthouse

noun3

1. •
   (historical) A house at a staging post: an inn with a stable where relays of horses could be changed, for stagecoaches or the mails.
2. •
   A company that carries out post-production.

   • Slow motion, fades, wipes, and text — once only affordable for major broadcasters and posthouses — now allowed DIY video producers a more polished, professional look. — 2013
3. •
   (no longer used) A building for distributing mail; a post office.