They also started using new IPs without PTR records to send out mail. Though so has Microsoft just recently. Both heavily frown upon that when receiving mail themselves. Do as we say...
Whether or not viable alternatives exist, those alternatives don’t magically change org structure, office politics, budget, current business priorities, etc.
Bottom line: many people managing exchange don’t have the luxury of evaluating this problem in terms of alternatives.
People used a few different groupware solutions, worked with bespoke IMAP installations on Linux servers, or (the vast majority) had on-premises Exchange servers running locally. It all required lots of tech wizardry, tinkering, duct tape and hope.
It was a long while before we had turn-key solutions, and you needed actually knowledgeable folks running your IT operations, and nothing was as fully integrated or cheaply available as Exchange Online.
a.k.a. i think you're missing the point. It's ok. You want knowledgeable people running your key infra. Outsourcing that to a company that doesn't respect privacy seems to be shooting oneself in the foot.
IIRC as they've been acquihired they had their own software stack back in 90's.
Getting email right requires lots of infra expertise, steady financial expenses, and time. Most companies just don’t have any of these available, and it makes zero economic sense as well if a product like Microsoft 365 exists.
Microsoft being annoying and frustrating and having so many issues is why I have a well paying job in IT.
But things like icloud, office365, google workspace and similar are "too big to fail", right? They don't have to play by the same rules as the rest of us peons.
as referenced here, from the post on the 'mailop' mailing list
https://news.ycombinator.com/item?id=43512353
This is either an astonishing level of technical fuck-up from what has to be an entire work group of people with six figure salaries whose jobs are nothing but running email server infrastructure, so they must clearly know better, or a lack of regard for the internet community and accepted standards. I really cannot think of a third possible explanation for it.
To be clear for those people who don't run their own email servers: Having proper reverse DNS for the IP of your outbound SMTP sending server is one of the absolute bare minimum requirements for accepted mail flow, and is a standard that's probably 25 years old or older now. It significantly pre-dates SPF, DKIM, DMARC and all the rest. Proper RDNS is literally one of the first things you verify before you set up everything else.