My domain used to be fastie.net. I've been using fastie.com for many years now and when the .net address expired a couple of years ago, my brother took it on. My associated email addresses have been turned off for about two years.
A few site or service registrations still exist with the old addresses and, not having them active, it is very hard to make changes. Sensibly, companies attempt to validate any change using the email address they have on file. Recently my son brought this up regarding his Xbox account. Because my brother does have the domain, I asked him to set up some forwarders for my family's addresses. He asked about mine and as an afterthought I said yes.
Mail to that address immediately started arriving.
That's a good thing because I've been able to catch up with some old friends. It has brought some junk out of the wilderness but that will vanish when I turn the addresses back off.
I often worry about the fragility of digital data. Maybe I shouldn't so much.