Hello,

I would recommend going through the DigitalOcean Terms of Service, mainly under the Email Violations section here:

https://www.digitalocean.com/legal/terms-of-service-agreement/

It is stated that users shall not send bulk email utilizing their resources on the Services unless they maintain a double-authorized list of subscribed members including IP addresses and relevant contact information, along with following guidelines for including removal links with all sent emails according to the such legislation.

Regards,
Bobby