I am having issues when users are sending appointment from Outlook
2007 that other users cannot respond to.
I am running a mixed mode of Exchange(on internal server) and POP3
(externally hosted). Internet email goes through the POP3 account.
Exchange is only used for internal calendars, contacts and tasks.
However, we rely on Internet email to send out invites to meetings
and
assign tasks as not all users are be on Exchange. When someone
invites an attendee from Outlook 2007, it is sent to other users
(predominately Outlook 2003) fine. When they reply, they get an
undeliverable because it wants to send the response to the Exchange
mailbox which is not possible due to the current set-up of Exchange.
We do not allow sending mail on Exchange as it would build up and
folks would miss their mail.

I want to be able to have the appointment reply to the Internet
address of the client who sent the original appointment request. Not
to the exchange address.

Any help would be greatly appreciated :-)