Exchange Server 5.5 beta hits Web. Computer Reseller News, September 22, 1997. IMAP Enhancements Are In The Mail. InternetWeek, September 22, 1997. VAR Business, September 15, 1997.
Nothing's free, but intranet comes close.
PC Week Online, September 8, 1997. InternetWeek, September 1, 1997. InternetWeek, September 1, 1997. Domino's Got New Clients. Windows Sources, September 1997.