What do you mean by "stay in their network", when it comes to sending emails? Google is not in the business of being a paid mass email sender for businesses. Wh

What do you mean by "stay in their network", when it comes to sending emails? Google is not in the business of being a paid mass email sender for businesses. What business email they handle is specifically for being the email host for a business's internal email, not sending their newsletter / marketing / account notifications / whatever else.