I used to get email for an org that had a similar domain as me (they had an extra letter in the middle). Thankfully, not a very big org, I would just bounce addresses that got a lot of misdirected email and I think they shut down and that really solved the problem.

Still annoying, but not as bad as gmail. I just got an email, in Italian, about someone adding a passkey to their ebay account. No way to tell ebay it's not their address / it's not my account.