1 Log into your
Mail Gun account
2 From the top menu click "Bounces".
3 In the "Webhooks for the current domain" box, enter the full url (starting http://) to the following file in your responder installation:
web-hooks/mailgun.php
(http://www.example.com/web-hooks/mailgun.php)
Note: For security, you may rename the above file.
4 From the top menu again click "Complaints". Repeat step 3.
5 Finally, click "Set" for both options to save.
Web hook is now set up.