Hey @markwilde ,
With how things are configured at DO (no FQDN etc.) the addition of a PTR record isn’t actually possible. I think the best solution here is to make use of a URL shortener, masker or intermediary like most large subscription email services provide by default.
The only alternative, given constraints, is to reach out to each spam list vendor on a case-by-case basis and discuss how our infrastructure works. Then, we’d need to reach out each time DO rotates an IP or we introduce new/different nodes with this vendor.
Sorry I don’t have better news for you!