>In the end it is Microsoft's problem, since they are the ones that are losing valid SMTP traffic. If a sufficient amount of users are experiencing a loss of e-mail as a result, then they will be forced to fix it.
One might think that would be the case eventually, but at least in the case of universities insisting on using Office365, it really doesn't seem to be. In academia, where emails to and from university domains are the norm, Office365 seems to frequently treat with extreme skepticism odd domains, like those with .edu or .org TLDs, or prominent universities on ccTLDs in Europe, assuming that most legitimate mail will come from inside an organization. I've seen it send directly to spam emails about papers, peer review, talks, emails from easychair.org, emails from major journals. I know of a case where it has sent emails from Nature's submission system to spam. I've seen it send emails from frequent collaborators to spam. Classifying emails as not spam seems to do little to nothing. Meanwhile, emails from major providers' email services, like gmail and outlook, often seem to get through, despite mostly being spam, and in some cases, rather obvious spam.
It seems likely that people have lost publications and talks as a result: the emails being rejected and spam-filtered are important emails. Yet as much as everyone seems to complain—and these are complaints I have heard from many people, at many universities—Microsoft seems to have continued success in selling Office365 to university IT services, and pushing everyone to use it.