The author points out real risks when running your own domain. When you host your own domain, you must treat that and its registrar as a risk vector like your inbox, including 2FA, locking domain transfer, auto-renew, backup email accounts, and update payment details. Like the author I too run my own email out of my domain, and I love the flexibility, but it requires vigilance.

One serious issue is how much email became the de-facto identity of the Internet. This is the ultimate reason why all the above is necessary.