I want to create a notification (or supervisor rule) on Freshdesk Mint when an agent reply to a ticket is sent but not delivered. This thread here says it's not available, while in your release notes it is stated "Mail delivery failure notification for compose email in Mint".
Can you please help me on how to send an email notification when a message is not delivered?
The documentation for the feature is in progress - we will update the article soon. The feature is live and the mail delivery notifications would be sent to the agent who sent out the reply. You will also notice the failure message on the ticket page.