Domain MTA Status in FortiMail has three possible statuses represented by color code: Â  Â Green: Reachable.
This indicates the MTA is currently reachable. If no further emails arrive, the green status will remain unchanged until the status changes.
Amber: Unreachable.
This indicates the MTA is temporarily unreachable. If delivery to the MTA fails, the status turns Amber after the 'Time interval for retry' setting is reached. Go to System -> Mail Settings -> Mail Server Settings -> Mail Queue to verify the configuration.  
FortiMail will continue retrying delivery based on the settings, and the status changes back to Green once the MTA becomes reachable.
 Grey: Not Enough Traffic.
This indicates that there has not been enough email traffic to determine the reachability status. | 
