Being marked as spam on all @hotmail, @outlook, @live, and @yahoo addresses

Receiving “Mail delivery failed: returning message to sender” messages on virtually ALL emails being sent to @hotmail, @outlook, @live, and @yahoo servers.

What types of modifications can I make to the message or the config file to help these servers not flag my emails as spam?

Here is the entire message:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its

recipients. This is a permanent error. The following address(es) failed:



SMTP error from remote mail server after RCPT TO:<[]>:

550 5.5.0 Requested action not taken: mailbox unavailable (S2017062302).

Any and all suggestions welcome.

Welcome to my world. I have DMARC, DKIM and SPF all set and still fall in the same hole. YAHOO decides who should be allowed to send mail and blocks all others.

Seems that Yahoo, Hotmail, Microsoft and Google set a kind of exclusive lobby.
It’s clear they would like to handle all the email traffic in their interests, someone of them with their personal and absurd black list.

No matter if you correctly setup SPF, DKIM, DMARC and MTA-STS on your own mailserver. You will always get some troubles.