DigitalOcean, or more precisely - some of their customers are the source of quite a few spam tsunamis, at least according to spamtrap data I'm collecting on my mail server. So from that perspective, a big "thank-you" goes out to DO for firewalling off outbound port-25 traffic by default.

That said - reading "Even if SMTP were available" and "recommend using SendGrid", it sounds like there is no opt-out from this. Even for customers who would want to self-host a mail server that never sends in bulk. Now that, is reprehensible, and adds yet another brick in the already tall wall that mail duopoly+ (gmail, outlook, and handful others) enjoy.