@julian can't be the API as I have checked it multiple times.
I have heard that MailGun got to be on the same IP/localhost as NodeBB/Computer (in my case VPS), is that true?

@julian I switched from MailGun to MailChimp/ManDrill as I don't think it works over a domain from Namecheap on a VPS hosted somewhere else, so I am testing that now first.

But I'll share the log error:
2020-09-04T08:16:34.862Z [4567/51466] - warn: [emailer.mailgun] Unable to send banned email to uid 1!!
2020-09-04T08:16:34.863Z [4567/51466] - error: [emailer.mailgun] (Forbidden)
2020-09-04T08:16:34.863Z [4567/51466] - error: Error: Forbidden
at IncomingMessage.<anonymous> (/home/kristoffer/nodebb/node_modules/mailgun-js/lib/request.js:309:15)
at IncomingMessage.emit (events.js:327:22)
at endReadableNT (_stream_readable.js:1220:12)
at processTicksAndRejections (internal/process/task_queues.js:84:21)

Hey.
I have setted up my Mailgun SMTP info on the Admin Panel but when I click "Send Test Email" nothing is sent to my inbox, I have also tried to use the Emailer-Mailgun Plugin but nothing is sent either.