It was flat out impossible for me to get Outlook to accept my mail server. They'd only give me some vague response with no actionable steps to resolve it. I gave up and used a gmail account to route everything outgoing. That way mail still shows up as from:jimm@jimm.horse but rides on Google's reputation. Defeats the purpose a little but there's nothing more I can do (apparently unless I buy my own non residential ISP line, host the server in my house, and build reputatiom forever, but that's an absurd length to have to go through. ideally we'd have antitrust legislation forcing MS et al to be fair towards smaller email and save the open internet overall, but I'm not holding my breath.).
Last time I tried to set this up, I think I was unable to get it for the super low advertised price, because they require you use an ec2 instance in order to skirt their minimum monthly charge and you can no longer get free tier ec2 after the first 12 months. so the monthly amount I would have to pay was going to be a non-insignificant amount.
I've been using it for over six years now, I'm always worried it'll stop working...but besides having to bump my node.js version a few times, so far so good, knock on wood.
It’s annoying but it’s definitely possible. You have to keep harassing the Microsoft’s support email, eventually someone will deign to read it and whitelist your specific IP address.
It took me a week of back and forth but I was eventually able to get them to allow my IP address in one of OVH’s banned blocks.
I'm guessing they are talking about outlook.com, which is one of Microsoft's alternatives to Gmail. I.e. outlook.com, a host of millions of email addresses, is rejecting the emails from their server.
https://news.ycombinator.com/item?id=35691618