It was known for its ability to interconnect several other APIs and protocols, including MAPI, cc:Mail, SMTP and MIME, and was originally based on the OSI standards such as X.400. In addition to email, it also supported directory, public folder, and contact-management functionality.
It was notable for being supported not only on HP-UX, but also on IBM's AIX, Sun Microsystems' Solaris and Linux, which increased its attraction for enterprise customers. There were also lesser-used versions for SCO Unix, DG/UX, Ultrix and Windows NT.
From the initial designs in 1987, OpenMail was primarily designed and developed at HP's now-demolished Pinewood offices, near Wokingham, England (also the home of OpenMail's predecessor product family, HP DeskManager and the original developers of HP NewWave).