PM emails, thread watch notifications, etc. are not considered admin emails.
You can remove email notifications for threads / forums by unwatching them and rewatching them without the option for emails. As for PCs, you can turn them off in your preferences: http://xenforo.com/community/account/contact-details
@ScottLott: Then it should be very easy to implement an acp link at account info which does exactly the same.
A simple template edit would solve this issue.
I'm not sure how I would get the "email confirm key" outside of the email template, and I don't see where in the xf database is changed once this link is clicked.
I'd definitely want to setup a link I can send users (Unsubscribe from all email messages) that can be placed anywhere, including in their account settings.