It looks like development of Pegasus is coming to an end. Pmail brought desktop-friendly email to many users as our campus evolved to desktop PCs, connected by LANs and file servers (Novell) which were then connected into a campus-wide internet.
As time went by, Pegasus (actually Mercury probably), became a source of annoyance with issues like only being able to forward email to an IP address and not a host name (and thus not being able to take advantage of our DNS round-robin balancing and DNS fail-over processes at the time).