How to set up Exclaimer Cloud in a hybrid environment using centralized mail flow

1. Sign in to the Exchange Online admin portal (https://admin.exchange.microsoft.com) as an Administrator.
   
   The Exchange admin center is displayed.
   
   
2. From the left-hand navigation menu, select mail flow, then connectors.
   
   
3. Reconfigure the hybrid send connector to apply Only when I have a transport rule set up that redirects messages to this connector.
   Example:
   
   
   
4. Leave all other connector settings as they are and save the connector.
   
   

1. In the admin center, under mail flow, select rules.
   
   
2. Click Add a rule (+ plus button), then select Create a new rule. 
   
   
3. Give the rule a name - for example: Send on-premise.
   Example:
   
   
   

1. In Apply this rule if, select The sender. In the adjacent box, select is external/internal. In The Sender is located, select InOrganization. 
   
   
2. Click Save.
   
   This will ensure that all emails sent from your Microsoft 365 tenancy are routed through the connector.
   Example:
   
   
   Now, add an action that states Redirect messages to the following connector and select your Hybrid Send Connector.
   
   
3. In Do the following, select Redirect the messages to. In the adjacent box, select the following connector. In select connector, select Select your hybrid connector. 
   
   
4. Click Save.
   
   Example:
   
   
   
5. Click + to add an action.
   
6. In Add, select Modify the message properties. In the adjacent box, select set a message header.
   
   
7. Click Enter text and set the message header to something, like 'x-sentonpremise' and set Value to 'True'.
   
   
8. Click Save.
   Example:
   
   
   Now, add an exception for 'A Message Header' that 'Matches these text patterns' and set that rule to also be for the text  'x-sentonpremise' and Value to 'True'.
   
   
9. In Except if, select The message headers.... In the adjacent box, select matches these text patterns.
   
   
10. Click Enter text and set the message header to something, like 'x-sentonpremise' and set Value to 'True'.
    
    
11. Click Save.
    Example:
    
    
    This combination of adding the header and setting it as an exception means that if the mail is returned to your Microsoft 365, it will not be redirected to the connector again, preventing mail loops.
    
    
12. Click Next to set the settings for the new transport rule.
    
    
13. As required, fill in the options and click Next.
    
    
14. Review and finish creating the new transport rule.
    By default, it is turned off until you turn it on from the Rules page.
    
    
15. You will see the new transport rule in the rules list with a priority of 2. The Exclaimer rule called Identify messages to send to Exclaimer Cloud has moved to a priority of 1.
    
    Your Microsoft 365 set up is now complete.
    
    NOTE: Please allow up to one hour for mail flow changes to replicate in Office 365.

The final step of this process is to return to the Exclaimer Cloud portal to ensure that emails are routed to Microsoft 365 once the signature has been applied:

1. Log in to your Exclaimer portal.
   
   
2. Select Launch for your subscription.
   
   
3. Select Settings in the Cloud portal.
   
   
4. Select Mail Flow.
   
   
5. From the Mail routing mode drop-down list, select Static Domain.
   
   
6. In Domain name, enter your .onmicrosoft address (listed in your Microsoft 365 tenancy under Domain Name).
   Example:
   
7. Click Save to save the changes.
   
   Your setup is now complete.