Restrict ticket creation via email from contacts only

I’m trying to find a way to configure the system so that only emails received from valid contacts create a ticket. There doesn’t seem to be a simple way to do this (a huge hole in functionality if there isn’t). Given that creating an automation where every single contact has to be listed individually is impossible at scale, how can I do this? If I disable fowarding from our support email address then a customer loses the ability to reply to an email ticket thread, which is unacceptable.