Why email signatures look different in Apple Mail when using Metadact

Scenario

Why are Exclaimer signatures not displaying correctly on Apple Mail clients (macOS and iOS)?

Reason

Metadact reprocesses the email after Exclaimer has added the signature and logo, which causes the signature to display incorrectly in Apple Mail.

Resolution

To resolve the rendering issue on Apple Mail:

Update the Metadact rule by adding an exception that ensures Metadact skips emails already processed by Exclaimer.

1. Log in to the Exchange admin center using your Microsoft 365 Administrator credentials.
    
2. From the navigation menu, select Mail flow, then select Rules.
    
3. Locate and select the Metadact transport rule.  
    
4. Select Edit rule conditions. 
    
5. In the Except If section, select + to add an exception. 
   
   
   _{Select + to add an exception.}
   
   A new exception row is added at the bottom. 

6. Set the message header to:

   X-ExclaimerHostedSignatures-MessageProcessed
7. Set the value to True.
    
8. Make sure the Metadact Transport Rule has a higher priority (a lower rule number) than Identify messages to send to Exclaimer Cloud Transport Rule. This will ensure that the Metadact processes the message before it is sent to Exclaimer, and Exclaimer applies the signature after Metadact has completed its actions.