Dear Experts and Gurus,

I hope someone can offer helpful advice ? I've been trying to trace some odd events encountered by an Outlook 2007 user.
Basically, when he send meeting invitations to external contacts at one particular customer, the response received is set to 'tentative', which is plausible, but the peculiar part is that the external contacts' address is changed to our domain, overwriting theirs.
Example: "[email protected]" sends an invitation to "[email protected]". The tentative response appears to have come from "[email protected]" !!

Any advice on a simple way to trace this would be appreciated. Please note that 'normal email' between sid and bob is working correctly and traces in the exchange server logs clearly show the 'normal email' is fine. This only happens with calendar/meeting requests and only for one external domain.
Thanks to you all for your patience and guidance.
Bren