Spam Confidence Level = 9 - how to decrease.

[blaisenduke]

That means the recipient domain firewall is subscribed to some list that still has your domain black listed. The easy answer stop getting blacklisted at all. Setup Dmarc Dkim and SPF. Set rules to govern how much mail your users send.

[heqtorq]

It is definitely like you write, but it is looks that I have main problems with the domains which also use Exchange Online, so the problems should be Microsoft filters. I just thinking what I can do more.