403 Error

When subscribers are sent the confirmation email, they get a 403 Error when clicking the link. What is the solution for this?

What link you are talking about? I assume you are talking about the link to activate user account? If that's the case, I think 403 error happens because user registration is disabled and Joomla throws error when users try to activate his account

To prevent that error, go to Users -> Manage, click on Options button in the toolbar, set Allow User Registration parameter to Yes and the error should be gone

Regards,

Tuan