Granted, this is a bit belated, but you should know that Outlook Web Access (OWA) just recently turned 10 years old!
On May 23, 1997 we have released Exchange Server 5.0. The product contained a Web based e-mail interface which was originally called "Exchange Web Access". Later on, we have changed the name into what we use today, Outlook Web Access or colloquially, OWA.
Thanks to David Espinoza for keeping track of this kind of stuff!