He’s right, but IMO all that automation needs to be managed client-side, but most of it should be implemented server-side.

So, you would need a protocol for the client to speak to the server and communicate what needs to happen. And while Sieve exists, most IMAP clients don’t speak it. And most IMAP servers don’t implement it.

I, for one, do not want this intelligence about my mailbox, to exist only on the server side. The server needs to understand how to carry out the things it’s told to do, but the real intelligence needs to live client side — and be mobile to other accounts at other providers.

Most importantly, no third-party SaaS should be involved.