I know its also strange for me..
But i found a work around!
(just 10 Sec ago..)
i added the internal ip of the exchange to the /etc/hosts.
127.0.0.1 phunix02 localhost.localdomain localhost localho$
::1 phunix02 localhost6.localdomain6 localhost6
10.0.0.101 phunix02.ltd phunix02.2contact.ltd localhost
127.0.0.1 mail.2contact.nl mail
10.0.0.12 2contact.com mail
And now it works!