You can't run a business where the 2 companies that control the vast majority of email can block you for no reason, and absolutely no visibility that something is wrong until a customer directly contacts you that they are not receiving email (and how would they even know in most cases unless they knew a message should have come through?)
Google was blocking signup emails to me from the 2nd largest telecommunications company in Australia at the time, and I ended up having to use my work address.