In which email inbox do you expect the email?
When you change the email address of an admin, the first confirmation email is sent to your current email. After you confirm that, another email is sent to the new address, asking you to confirm the new one.
Requiring you to confirm the old address prevents someone who gained access to your admin account from being able to change the email address which is, for example, used to receive the link to download a full backup of your forum.