UPDATE! You just have to open up a support ticket and complain enough for them to unblock the ports. I can confirm that the test mails now send and all seems to be working now.
DO Customer Support Email
Hello there,
We are following up with an update.
Our security team has unblocked the SMTP ports on your account.
You should now be able to configure them, but if you encounter any difficulties, please let us know so we can investigate further!
We're always happy to help if you have additional questions, so please don't hesitate to let us know.