Warn Clients Not to Use Domain-Based Emails for Account Communication

Hi team!
We’d like to request a warning that recommends clients not to use email addresses based on their own domain (e.g., user@domain.com.au) when signing up or updating their contact details.

There are plenty of recurring issues where:

A domain is in the process of being transferred to us (e.g., http://bloomsbymia.com.au/), and the client’s email (info@bloomsbymia.com.au) becomes temporarily non-functional during the DNS propagation or hosting transition.
ex. https://admin.worldhost.group/admin/clients/52d137e0-8d24-103e-2161-c3495163789e/products/0d1639e2-37d4-3523-6e89-f64610589e57/96e02e51-36d4-29d0-98e0-c1429807875d/overview
As a result, client is not receiving critical account or billing/support emails, ticket updates.
In other cases, a domain expires and the associated email becomes unreachable, effectively locking the client out of their account and making recovery difficult.