Technically you do not have an Alfred account if you connect your Google account with Alfred. Instead, you grant us access to the essential parts of your email account that we need for Alfred to work. Therefore, all you have to do is revoke Alfred's access to your email account. For Google accounts, here's how you revoke access.
If you do sign up a Alfred account with your non-Google email, please contact us on the feedback form and let us know which account you no longer need it. We'll process your request as soon as we receive your request.
Feel free to read more about how Alfred protects your privacy if you're interested.
Still have questions? Let us know on the feedback form