I locked myself out of my main email account once.
I had set it up in the year 2000, when people didn’t have mobile phones, so they sent a letter to your home address before they activated it.
In the meantime, I had moved 11 times, updated my personal info on the site a few times, but never added a phone number or recovery mail address.

So when I called the hotline and they asked me for my address to confirm I’m me, that was a hard one to answer. But I actually got it right in the second try, which was good enough.