RSVP not working in UWC

When I am creating a new event in the calendar tab of UWC and I add invitees, they don't recieve an email notification of that new event. The event shows up in their calendar but unless they know to go look for it they don't know it is there. Any ideas of where to look?

Here are my versions:

UWC: 122793-12

Calendar: Sun Java(tm) System Calendar Server 6.3-1.01 (built Apr 24 2007)

Mail: Sun Java(tm) System Messaging Server 6.3-1.04 (built May 9 2007; 32bit)

libimta.so 6.3-1.04 (built 00:41:36, May 9 2007; 32bit)

SunOS mail 5.10 Generic_125100-10 sun4u sparc SUNW,Sun-Fire-V490

Message was edited by:

sheger77

[671 byte] By [sheger77a] at [2007-11-27 9:56:18]