In daily practice you don't. Unless you host in a DC with lots of spam. Use small but trusted hosters.

But as long as you get SSL/DKIM/SPF and the other stuff right, and it's not THAT difficult, then most hosters will let you through. Unless it's German Telecom, because for some reason t-online.de decided to only allow emails from hosters they whitelisted and there's a whole approval process which even requires registering with them with an email that is NOT from your domain and even a fax, but honestly fuck anyone using that domain.