Have trouble connecting mail server (mailgun)

Hello community I have a little trouble connecting mail server

I set this up like the picture above but still have no connection

The annoying thing is I cannot put more than 1 dot in hostname when I use type CNAME

FYI, I tried host name “forum.yonstreetbets.com” in TXT type, but it didn’t work

If you’re hosted by Discourse then you don’t need mailgun.