I do not have first hand experience.
It sounds like they insert an unsubscribe link and that a special header is required to make it go away. I don’t know if there is a way to have elastic email but a webhook to notify discourse of unsubscribes,but they are not listed in Handling bouncing e-mails.
I think that if you can make aws work, it’s probably the best solution, but that’s not a good solution for people who come here to learn how to make email work.
Mailgun is really easy.