Outlook 2k chooses the wrong email-adress

[Nils]

Hello everybody,

I've got a problem with my Outlook 2k.

Some of my contacts have more then one e-mailadresses. One of these adresses
are
marked as standard.

My problem now is the following:

When I'm writing a mail to one of these contacts, but NOT at its
standard-mailadress,
Outlook changes this adress to the adress I've defined as standard and sends
the mail.
This happens even if I'm typing the adress, not choosing it from the
adressbook.

Deactivating the option "test names" doesn't even solve this problem.

I'm working with Microsoft Outlook 2000 - SP 3, Version 9.0.0.6627.

Does anybody know anything about this problem?
What do I have to do, to solve this problem?

Thanks in advance
Nils