Outgoing emails marked as SPAM and Phishing emails by O365 servers

I've been through this now two times. 

Every email containing my domain was marked as high confidence spam on every O365 tenant I know. On my own, as well as on customers. Even at the bare minimum, a plain text email containing just "myDomain.org" was marked as spam. 

I knew about some spam incident involving our domain as an email sender from non O365 servers that fits around the starting time of the issue at the first occurence. For the second incident there is no realted event known to me.

Both times I have been hours in the Hotline with supportes that were honestly friendly and trying their best but tried everything to not move my ticket to second level support. They stick to their checklist and did not really take care of my mentions. E.g. he tried thousand times 'https://www.myDomain.org' at mail rules and stuff, even i showed him dozent times 'myDomain.org' was sufficinent. 

Both times it seemed to resolve itself after roughly 7 days, which lets me think their internal filters drop after one week. Support guy told me that they were working hard on my ticket and someone fixed it...

After the supporter saw the issue resolved itself the ticket was closed. Definetly not satisfiying. 

There is some panel the support guy pointed me towards: https://protection.office.com/reportsubmission where you can submit URLs that should not be marked as spam. If this is any good? Idk. 

Not sure if this has already been posted here, but another good link I found about this:

https://www.reddit.com/r/Office365/comments/ev98sd/an_issue_with_a_microsoft_office_365_customers/

So i am sitting here, waiting for the next time this starts to happen...