My apologies, I conflated two different posts together. Following the original post, I had also shared this update:
I had read the post you shared, and it’s odd that SMTP mailing isn’t working for you with Microsoft, because the post does state that SMTP would be unaffected by those changes:
If this still doesn’t work, you may not necessarily need to use a mail relay service if you’re able to install something basic like sendmail on your server, and use that, rather than an external SMTP service.