Sending directly from a Digital Ocean VPS? Yeah good luck with that bounce rate.

I use SendGrid free on Azure because Azure VPS too have an extremely high bounce rate. Setting up an SMTP server isn't exactly hard or expensive (regardless of if you're integrating mailing lists or not), it is the good rep' IP address and making it "someone else's problem" to deal with a lot of email related problems (poor reputation, blacklists, random host decides to block you, etc) that you're paying for.

Sendgrid, Mailchimp, and so on primarily exist so you can just hit send and then that's as deep as your involvement goes as far as emails.