Hello Developer,
Apologies for late reply, Mailgun service is only avaiable with Markettng Automation product, you can not bind this along with App42 Email Service. In order to configure your mailgun inside App42 Dashboard, please select App42 Cloud API product from dropdown which is on the top of header and click on Unified notification -> Settings -> Email to configure mailgun.
P.S As of now, App42 and mailgun is provided in the dahboard. If you face ny issue while integrating, just let us know.
We are happy to help you!!!
Regards,
Himanshu Sharma