I do not have an email address, can I use my XXX's to register?
NO. Your account might contain your sensitive information such as your draft Will, which if you register with your Son / Daughter / Wife/ Uncle / That Random Guy Called Tim, then Son / Daughter / Wife/ Uncle / That Random Guy Called Tim could potentially access the information.
Always use the client's actual genuine email for sending the Will. This ensures security and direct access for clients. Do not use email addresses belonging to someone else, including email aliases (e.g., joe+will1@gmail.com, joe+will2@gmail.com), or fake temporary email addresses as substitutes.
Temporary emails may be accessible by unintended third parties granting them access to the user accounts which contain sensitive data, while using another person's personal email / email aliases exposes the individual to additional risk.
For the CEP, creating new emails for clients is acceptable under specific circumstances, such as when a client is not tech-savvy, provided the client ultimately controls the email account (e.g. the email's username and password should be given to the client and advise the client to change the email password accordingly)
It doesn't take long to create another email address, personally, I like Gmail so here's the link if you like to have one or you can use Proton mail.