How to set-up HA (high availability) cluster w/ ext DNS and backup MX

hi Josh et al and thanks for making running an open source software based mail server more user friendly :smile:

I read through a lot of docu (thanks for this!) and was wondering what your thoughts were on a high availability setup with externally hosted dns (eg dyn or cloudflare) and a backup mx provider (eg SpamHero)?

Thanks,
Axel

Iā€™ve never needed it.