Message Handling System
Novell's MHS (Message Handling Service) was an important early email protocol.
Originally developed by Action Technologies, Inc. (ATI) in 1986, it was first licenced, then later bought outright by Novell.
Role as a gateway
MHS was a very 'open' system, and this, with Novell's encouragement, made it popular in the early 1990's as a 'glue' between not only the proprietary email systems of the day such as PROFS, SNADS, MCI, 3+Mail and ccMail, but also the competing standards-based SMTP and X.400 - however by 1996 it was clear that SMTP across the Internet would take over this role.
A compatible range of gateway products called Connect2 from Infinite Technologies (now Captaris)[1] was also very widely used as part of MHS-based email networks.
Email clients
Pioneering Wndows-based da Vinci email and the free Pegasus Mail client both used MHS as their native protocol.