Initial situation:

Emails from the SEPPmail Secure E-Mail Gateway can no longer be transferred back to Exchange Online (ExO) in an Office/Microsoft 365 environment. In the Logs, the message

 

451 4.4.62 Mail sent to the wrong Microsoft 365 region. ATTR35.

 

can be seen in the detail view of an affected email.

 

Solution:

Via the "PowerShell Gallery" (see also www.powershellgallery.com/packages/SEPPMail365/), the current version of the "SEPPmail365 module" should be imported into the PowerShell.

Subsequently, first the existing, SEPPmail Secure E-Mail Gateway-related ExO rules and then the connectors are to be removed via this module.

Once these are deleted, first the connectors and then the rules are created again using the "SEPPmail365 module".

 

The documentation can be found in the chapter SEPPmail365 Powershell Module.