Ignore email from some customers

We’re in the process of migrating to Syncro but for now we are using another ticketing system for most of our customers and have a few customers that we’re using Syncro for. That said we are creating every one of our customers in Syncro so that we can move all of our customers’ assets into Syncro so I’m setting up customers and loading in all of their contacts. I have email setup to only process inbound emails for known customers. Is there a way to take it a step further and turn off creating tickets for customers on a customer by customer basis? I’ve tried deleting the auto-generated email rules for the customers I don’t want tickets to ingest for, but that doesn’t seem to work right.