Hey @trybizrep,
I think that you can input a Unsubscribe Group ID in the default “Send Email” in Bubble. However, I’m not sure how reliable it might be since Bubble uses Sendgrid and SendGrid isn’t too reliable from experience.
When sending newsletters the major thing you need is a way for your users to unsubscribe. I personally recommend using Postmark because they have transactional emails along with broadcasts (marketing).