[lxgr]

> With this solution, there's a high chance that if they ban you by mistake (AI bots are to blame), they will not disable the forwarding mechanism.

Why bet on that instead of doing it the other way around (i.e. making the self-operated mail server the primary that forwards to the service provider inbox), or at least practicing doing so by pointing the MX records accordingly?

[pseidemann]

Afaik sending emails is much harder than receiving, because of several layers of anti-spam measurements, which don't apply for receiving (besides local spam filters).

[lxgr]

Yes, but send and receive paths don't have to be symmetric. It's perfectly fine to send via the third-party provider and receive to your own server and forward to the third-party provider.

The forwarding MX would need to support things like ARC and DKIM, though, or the forwarded emails themselves run a high risk of getting dropped as spam by the third-party provider.