How to ensure emails are routed to Exclaimer Cloud before being routed to third-party security solutions

1. Log on to the Microsoft 365 Portal as a Global Administrator.
   
   
2. Open the admin center.
   
   
3. Click admin centers and select Exchange.
   
   
4. Select mail flow then select connectors.
   
   
5. Reconfigure the connector to apply Only when I have a transport rule set up that redirects messages to this connector:
   
   
6. For all other third-party solutions, leave all other connector settings as they are and save the connector.
   
   
   For Barracuda: reference extracted from How to Configure Office 365 Outbound Automatic Replies.
   

   1. Click Next then select the Route email through these smart hosts option and click the + symbol.
      
      
   2. Go to the Barracuda Email Security Service, and click the Domains tab. Copy your outbound hostname from the MX records, and enter it in the add smart host page:
      
      
      
   3. Click Next. Use the default setting, Always use Transport Layer Security (TLS) to secure the connection (recommended) > Issues by Trusted certificate authority (CA):
      
      
      
   4. Click Next.
      
      
   5. Validate the email - enter a test email address and click Validate. Once the verification is complete, click Next.
      
      
   6. Review the connector settings and click Create connector.

1. In the admin center, under mail flow, select rules.
   
   
2. Click the + (plus) button to add a new rule.
   Example:
   
   
   
3. Give the rule a name; example: Send to Mimecast.
   Example:
   

1. From the Apply this rule if drop-down list, select The sender. From the adjacent drop-down list, select is external/internal.
   
   Example:
   
   
   
2. From the select sender location drop-down list, select Inside the organization. This will ensure that all emails sent from your Microsoft 365 tenancy are routed through the connector.
   
   Example:
   
   
   
3. Click Save to save the changes made.
   
   The changes are reflected in the Set rule conditions window.
   
   
   
4. Click + (Add condition) to add another condition. 
   
   
   
   
5. From the And drop-down list, select The recipient. From the adjacent drop-down list, select is external/internal. From the select recipient location drop-down list, select Outside the organization. 
   
   This will ensure that your internal emails sent from your Microsoft 365 tenancy are not routed through the connector and prevent mail loops.
   
   
6. Click Save to save the changes made. 
   The changes are reflected in the Set rule conditions window.
   
   
   
   
7. Now, from the Do the following drop-down list, select an action that states Redirect the message to.
   
   
8. From the adjacent drop-down list, select and select the following connector.
   
   
   
   
9. From the select connector drop-down list, select your third-party Security connector.
   
   
10. Click Next.
    
    
11. The next step, Set rule settings is enabled.
    
    
12. Tick the Activate this rule on option and select a suitable time to activate the rule.
    
    Example:
    
    
    
13. Click Next. 
    
    
14. Click Finish. The new mail flow rule will be displayed in the rules list with the lowest priority (the greater the number the lower the priority).
    
    You will also see an Exclaimer rule called Identify messages to send to Exclaimer Cloud - this rule usually has a priority of 1.
    
    Example:
    

1. In the rules list, please ensure there is a tick against the Identify messages to send to Exclaimer Cloud rule for Stop processing rules.
   
   Example:
   
   
   If it is not ticked,
   - Select the Identify messages to send to Exclaimer Cloud rule. 
   
   The Identify messages to send to Exclaimer Cloud rule is displayed on the right-hand pane.
   
   - Click Edit Rule conditions.
   
   - Click Settings.
   
   - Tick the Stop processing more rules option.
   
   - Click Save. 
   
   Example:
   
   

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

1. Log into the Exclaimer portal (portal.exclaimer.com) and Launch your subscription.
   
   
2. From the left-hand pane, click Configuration, then select Manage Mail Flow.
   
   
3. In the right-hand pane, under Mail Routing Domain, are the relevant options.
   
   
4. In Domain Name, enter the .omnicrosoft.com domain name - this can be located in the Domain list in the Microsoft 365 Admin Center. This setting is important, and an incorrect domain can result in mail flow issues.
   
   Example: 
   
5. Click SAVE to save the changes made. 
   
   Your setup is now complete.
   
   NOTES: The MX record for the Domain name (in the Mail Routing settings) should specify a single Exchange Online Server for your Microsoft 365 tenancy. 
   
   - To check the MX record for your own Domain name, use a DNS lookup tool, such as MXToolbox. 
   
   Example showing Exclaimer's domain:
   
   Your setup is now complete. When you send a test email, you will be able to see (from the message headers) that the email routes from Microsoft 365 to Exclaimer Cloud, then from Exclaimer Cloud back to Microsoft 365 and from Microsoft 365 to Mimecast - as expected.