G DATA 365 | Mail Protection

If the G DATA 365 | Mail Protection has been set up so that the MX record points to mailprotection.gdata.de, emails redirected from Outlook cannot be processed correctly. This is because Outlook sends exactly this e-mail back to us. Since we have already scanned this e-mail and it is known to us, it will no longer be accepted in order to avoid loops.

In this case, change the type of rule in Outlook.
Instead of redirecting the e-mail, create a forwarding rule in Outlook.
So Outlook sends us a new e-mail that has not yet been scanned. This e-mail is accepted, scanned again and forwarded.