Honnored Experts and fellow geeks :-)
I have a customer with a strange problem (always strange problems from customers)
Recently they installed a new Server 2012 as a member server with Exchange 2013.
At least once every day the server seems to reject mails giving senders a Non Delivery Report saying:
#554 5.4.4 SMTPSEND.DNS.NonExistentDomain; nonexistent domain ##
If you simply restart the server everything is working fine for some hours.
Can anyone give me some clues?