New ask Hacker News story: Ask HN: My large scientific research org is on the Microsoft spam list. Advice?

Ask HN: My large scientific research org is on the Microsoft spam list. Advice?
2 by pruepp | 0 comments on Hacker News.
Dear HN, due to some successful phishing attempts at my organization with over 2k personnel, we've been blacklisted by Microsoft, which causes valid e-mails to their domains being rejected. This is a substantial problem, because it prevents a lot of scientists (and administration) from being able to efficiently communicate over the mailing-lists, and the like. Our ticket system is still been flooded about this and although it is not my responsibility, I wanted to ask: why is it so easy for a three-letter domain, that's been online from the dawn of the Internet to get blacklisted so easily? Even a simple WHOIS request yields a "Changed" record stating 2017. Is the rejection list based on IPs? Is there anything preventing the usage of a more differentiating algorythm? The respective requests to fix the problem have been sent, but it's been at least a week already and the havoc is real. Please share your experiences and/or advice. Thank you!