@Scopeman Thank you for your advice. This is all working fine when the Windows clients have joined the domain. The problem is, that if the clients haven't joined the domain (working as a workgroup computer which I prefer in a small company) then mydomain.dk does not point to the Exchange server and thus SERVER.mydomain.dk cannot be resolved even though the client pcs DNS server have been set to the IP address of the Exchange server! Any suggestion would be greatly appreciated
This part confuses me ... is your setup a single server running Active Directory, DNS and Exchange all on a single server? Really not a good idea if that's the case. If not then why would you point client DNS servers at a server that is not running DNS ... nothing will resolve. Can you ping the address autodiscover.damese.dk from your client? What mydomain.dk points to is irrelevant to what SERVER.mydomain.dk will point it ... DNS can point them to different IP's. I know these questions may seem simple but without more information we are going to struggle to guess setup. Even on a small company, it would be better to join them to a domain so you can control the various settings from the server via GPO's etc.
Yes, the setup is a single server running AD, DNS and Exchange. This setup has been working fine for years in small companies employing just a few people. And no, I could not ping SERVER.damese.dk on the Windows 7 client. However I repeated the experiment on a Windows 10 client, and now I can ping both SERVER.damese.dk and damese.dk which resolves to the server I have to look into it again, thanks