Emails are apparently working but they are not really sent

I have send some emails (registration, password forgot and even test mails) and all seems to be working.

In console:
Started GET “/admin/email/sent.json?offset=0&=1537948167257" for at 2018-09-26 07:51:42 +0000
Processing by Admin::EmailController#sent as JSON
Parameters: {“offset”=>“0”, "
Completed 200 OK in 39ms (Views: 0.2ms | ActiveRecord: 10.7ms)

And in web:

But they are not reaching inboxes (not even in spam folder).

I have tried with 4 different mailboxes (gmail, yahoo, and 2 POP accounts in different ISP’s). I don’t believe is something on “the other side”, but Discourse …

Any help ?

Thank you !

What email provider do You use to send emails?

Do they present any logs? If so, do the logs read any errors?

The SMTP logs error led me to this:

Thank you

Do you mind sharing your logs instead of troubleshoot article?