Send Email to a @mention user when a Internal comment is added to an issue

[Strong Tractor]

Hello, Please find my screenshots and I want to send Internal comment only to the every mentioned user like the JIRA Native functionality Email Notification does. 

What should be the value ges into "To" recipients section in this case? 

[Uday Kiran Bhaviri]

In Jira when you mention a specific user the user automatically recieves that notification if the user has the application and project level access(agents / admins/ any other roles)    or if the request has been shared with the user (Request Participants).

And if you are making a comment as internal it can be viewed by the agents or service desk team members or subsequent permission members.