Email address is already registered with another account

I am the domain administrator for @broadwayburrardchiro.com the domain has been verified and it's mx records are pointed to zoho.

Trying to add the alias drtyler@ broadwayburrardchiro.com and getting "The email address is already registered with another account which is not a part of this organization."

I've tried to login to the email address and recover the password, but it looks like drtyler@ broadwayburrardchiro.com is the admin account and the account is not forwarded so there's no way to get into the account. Is it possible to have drtyler@broadwayburrardchiro.com deleted so I can add it as an alias under the correct master account?

Please advise.