How do you mitigate the privacy risk of mail providers reusing email addresses for accounts when their customers stop paying for services? (e.g., I heard that f

How do you mitigate the privacy risk of mail providers reusing email addresses for accounts when their customers stop paying for services? (e.g., I heard that fastmail do this). For example, user@example.com signs-in to your site and stores data they expect to be private, they stop using the mail provider and the mail provider deletes the user's account which allows it to be re-used, then another unrelated user signs-in to the site and takes-over the account. I imagine the only viable way would be a whitelist of domains of mail providers that are known to not recycle email addresses (like Gmail), or to also check if the WHOIS data for a domain changed.