Seems to work for many websites. But only if your users aren't giving you money, because it's 50/50 whether they'll use a different email address or give up entirely.

As unserious as you claim, we had this exact problem.

Emails would be accepted by Outlook.com, but would never deliver. We had SPF/DKIM/DMARC and full reporting. They RBL'ed us with no remedy.

We told the customer to not use outlook.com BECAUSE we told them we could not guarantee any delivery of messages.