Comment by gwd

That's why TFA recommends buying multiple domains. He literally has a formula:

     (Desired Daily Volume / 60) x 1.1

He recommends that each domain have only 3 inboxes, and each inbox sends max 20 emails per day. So if you want to send 6000 emails per day, you should by 110 domains.

So block away! Unless you're using regexes, it won't make a big dent.