Have you tried to reach their customer service for any type of product? I don't mean free things like Gmail where you are the product, I mean things you buy with actual money, like phones or cell plans.
Gods help you if the problem you're experiencing is not resolved with a scripted response. Good luck if your Pixel phone needs repairs, or if your data plan is suddenly suspended for some weird reason. Enjoy playing "email ping-pong" where you wait a day between messages that ask you to do the same troubleshooting steps over and over.
Honestly restricting access to those that require it and going the extra mile to make your whole building a faraday cage would still seem basically fine to me.
You'd need to have a good way for people to get emergency messages, but it's a genuine security hole that could genuinely (it's not super likely but it's also far from impossible) cost your business a boatload of money.