How do I un-link my email address from someone else's Apple ID?

Like I said, I've had that email address for nearly 10 years now. Think about how long it would take me to change every single account connected to that address. There are dozens upon dozens. And then I have to tell all my contacts about the new address and they have to update it in their records. All so that I can have some obscure address that people are perhaps less likely to use accidentally, but not guaranteed to be any better. Not a great solution.

I guess I'll just filter it like everything else. But it's pretty standard practice by major companies to verify emails and/or offer an unsubscribe option, so I don't see why it's so difficult to unlink the account/email in this case.

Thanks for the suggestion seventy one, but to clarify, I actually already have a working AppleID linked to my email, so no issues there.

I've figured out what's going on, I think. The other guy's AppleID is (names made up) edward+daniel@gmail, but gmail ignores everything after the '+' and so when Apple sends email to edward+daniel@gmail, it goes to my account, which is edward@gmail. So, two different AppleIDs got linked to one email address. I figured this out because I tried to email him to let him know what was going on and it ended up in my inbox. So the issue seems to stem from an inconsistency with how Apple and Google determine uniqueness of email addresses including special characters like '+'. I imagine this happens with '.' as well as '+'.

I made up the names edward and daniel, it's not actually anyone's email address, so no need for concern.

In practice, I'm sure you're right that I would have fewer problems with a longer, more complex email address. But in principal, the problem remains. I could sign up for the Apple ID

1234.NoOneWillEverUseThisAddress.5678@gmail

and someone else could sign up for the Apple ID

1234.NoOneWillEverUseThisAddress.5678+1@gmail

and apple would have no problem with it, even though for all intents and purposes it's the same email address. So the problem is not just the ambiguity of my, to use Dahveed's words, overly simplistic and unsophisticated, email address:

there is a fundamental flaw in the way Apple links email addresses to accounts that allows for this ambiguity. If they followed the same conventions that gmail did, there would be no possibility of this problem.

To be fair to Apple, it's Google that isn't following the IETF standard for valid email addresses by ignoring the '+' symbol and everything thereafter. But there are close to 500 million active Gmail users, and Apple could, in probably just a few lines of code with one simple regular expression, disallow the registration of new AppleIDs that resolve to the same Gmail address.