When you realize you want full control over how your services are labeled.
For a lot of stuff, I just use dynamic DNS. But for email, you really need your own domain, although you can get a service to host it.
But if you want multihoming, DDoS protection, or DNS-layer redirecting or dynamic subdomains of your own, or a guarantee that the domain won’t vanish out from under you, you need your own domain.
When you realize you want full control over how your services are labeled.
For a lot of stuff, I just use dynamic DNS. But for email, you really need your own domain, although you can get a service to host it.
But if you want multihoming, DDoS protection, or DNS-layer redirecting or dynamic subdomains of your own, or a guarantee that the domain won’t vanish out from under you, you need your own domain.