Hi,
How to do threaded replies in parent-child or tree-leaf structure, similar to facebook, reddit, or hackernews?

Hi,
I have setup mailgun as email service provider from Admin >> settings >> Email >> SMTP Transport. It works perfect for few hours (number of hours yet to determine), but stops working after few hours. When I save the mailgun credentials again, it starts working and same thing happens after few hours.

What might be the reason behind this issue? How to solve this issue?