In which scenario would this happen, except for loss of ownership of the domain itself?
For instance, my main email address is on a domain that is now owned by my company (it wasn't originally). If I ever sell the company, I lose access to the domain as well. My wife's email address is on that domain too.
> my main email address is on a domain that is now owned by my company
I never mix work and private. My email addresses on my company's domain are for work-related things only. If I ever sell or close the company, it doesn't matter. I own a separate domain for personal email.
That's definitely a good idea. My company sort of emerged from a personal activity and things got mixed up. If I could do it again I would handle it differently, but you know, life's twists and turns... :-)
You can easily lose access any particular email address, even if it's on your own domain. Losing access to all your email addresses and phone numbers at the same time is far less likely.