This article on SendGrid is helpful. You do need to set up a separate MX record on a subdomain (or other domain) for inbound "parse" replies.
Connection to NodeBB was lost
I know this might be an old question, but I do did a research, and changed the json file, please check my url was fine.
Ghanks for any of helps
The source map url warnings have nothing to do with the "connection lost" error.
@pitaj yes you are right. Issue found, wrong redirect. Thanks