Integrating GroupWise with Outlook

[Preston Stephenson]

I send a meeting request from an exchange user to an exchange user.
In outlook when I accept the meeting, I get a popup dialog asking options in
sending a response.

I send a meeting request from groupwise to an exchange user.
In outlook when I accept the meeting, it just accepts the item and doesn't
prompt to send a response.

In groupwise, I'm sending an IMIP iCalendar meeting request.
Do you know what I am missing in the request that outlook doesn't prompt to
send a response?

I'm using Outlook 2003 and the server is Exchange 2003.
Thanks.