Microsoft Outlook email - Wrong recepient gets invitation W2k3 exch. 2003

Hello there,

The situation is this. Someone invites a person to a meeting, but when
the invitation is sent, a non-delivivery report comes in - from a non
existing user.

Of course I checked all the delegate permissions and rules, which were
not present. The recipient and te should-be-recepient are not related
by department, but their names are somewhat related.

For instance, a request sent to a user Miedema is being sent to a user
called M.Idema. A request sent to a user Jong, P is sent to a user
Jong, AJ (no longer in use).

There's nothing wrong with the email portion, it's just calendaring...
I found one or two similar problems on the internet, but no solutions
or explanations.

Any help would be appreciated.

greetings, Ralph