To prevent spoofing we added the folowing setting to the exchange server
Set-SenderFilterConfig -BlockedDomainsAndSubdomains atelxxxxx.xx
now any mails send from outside the mail server with the domain xxxxxxx = blocked.
I need to add one exception for this rule menaing that one emailadres info@xxxxxxx that is used for sending newsletters from an external mail cms software should be pas this filter settings. can anybody tell me how to do this?