Document DO policy regarding email servers
DO currently has a page called https://www.digitalocean.com/community/tutorials/why-you-may-not-want-to-run-your-own-mail-server
However nowhere in the doc does it call out the fact that, if you do it anyway, you will receieve no support from DO when the entire DO network IP ranges are blocked or DO ASN is blacklisted.
Currently the page only talks about the difficulties of running a mail server which any mail admin already knows about. It is not explicit on DO's own policies that impact anyone running a mail server on DO.
Even if a customer's email server is clean and not sending the mere fact you are running on DO can get you blacklisted and DO will not do anything to resolve the issue at their level.