I appreciate the concern. In my particular case, a strong spam filter currently seems desirable. I've (tried to) train spam filters in the past and that's one

I appreciate the concern. In my particular case, a strong spam filter currently seems desirable. I've (tried to) train spam filters in the past and that's one of the few reasons I was still relying on Google Workspaces up until recently was as one piece in a rube goldberg "megaprovider" spam filter. Though from what I see most of what Migadu is providing that cannot be turned off (SPF, DKIM, etc) are today considered best practices that you should add even if you were self-hosting, and the spam they prevent should be off your filters radar anyway, leaving your filter to better train on documents that aren't so bottom-of-barrel. (They are also, to my knowledge best practices to implement if you don't want to be entirely black-holed by the "megaproviders" as a self-host.)