Comment Re:Overkill??? (Score 2, Informative) 228
Actually, the mainframe can be sliced into logical partitions, LPAR. My guess is that they already had a mainframe which they use with one of the mainframe OS's to run their accounting, inventory, or manufacturing. They allocated a small LPAR for this, put Linux and the mail server software on it and voila, no more exchange.
The software they use (Insight Server from Bynari) allows running exchange type capabilities from outlook, so they replaced MS Exchange (which for 700 accounts is something like $50,000-$75,000 including OS, mail server, hardware for at least 2 intel boxex, CAL for both OS and Exchange), maybe more and not including Sysadmin, with this.