Disable Customer Email in Non-production

Summary

We are looking to quickly disable 100% of customer email function in non-production.

Content

The only functionality we know to turn off emailing is to update the customer email addresses to null or an internal address. Is there another system setting we can use to disable all emailing? We don't want to have to update massive amounts of customer email addresses each time we do a P2T.

This is relevant in non-prod because we don't want test emails going to customers.

Thanks!