rejecting email

Is there a working support address that subscribers with issues/problems can email? The typical "support" address is rejecting emails…

This is an automatically generated Delivery Status Notification

Delivery to the following recipient failed permanently:

Technical details of permanent failure:

Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 5.7.1 <>: Recipient address rejected: User unknown (state 14).

I’ll add that email, but for now, the following works: