Delegates perhaps?

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Milly Staples [MVP - Outlook]
Post all replies to the group to keep the discussion intact. All
unsolicited mail sent to my personal account will be deleted without
reading.
After furious head scratching, JobbyFactory asked:
| When user sents an invitation ( Outlook 2003 exchange 2000 ) to just
| one user and he accepts the meeting, this acknowledge mail is sent to
| the whole bunch of other users.
| The user has no rules set in his Outlook. Also he is sending from hos
| own MailBox