Apple id email address not available
My email address is not available, but I don't remember using it before?
Why would this be and how can I fix it?
iPhone 7, 15
"If you see a message that the email address you want to use isn't available or is already in use, check that you or a family member aren't already using that email address with a different Apple ID. If a family member is using that email address, remove it from their account then try to use it." From: Change your Apple ID - Apple Support
Apart from the above statement I have yet to find a formal Apple position statement online about re-using email addresses. Many user reports on this forum (of course they could all be just making up things but I don't have specific reason not to believe hundreds of independent topics over many years) suggest that contrary to what the statement implies as to ease of address re-use, if you have recently used an email address with Apple for another purpose such as a notification email address it cannot be re-used; at least not immediately and possibly never. I guess you can "try to use it" but many users have claimed this does not work.
About your Apple ID email addresses --> About your Apple ID email addresses - Apple Support