As an update on the email situation, the support page was updated with the following this morning:
01-JUN 09:00 UTC
We have confirmed that there are some issues for players using Yahoo when trying to make a Jagex Account, as there is an issue with Yahoo emails experiencing a delay in receiving email verification messages.
If you want to create a Jagex account using a Yahoo email address, please wait until this issue is resolved. Alternatively use another email provider for Jagex Account creation - you can always change your email at a later date if the issue is resolved.
01-Jun-2023 13:11:29