[fxtentacle]

I need server-side filtering rules that I can configure with a web UI. That basically leaves only Exchange and GMail. AFAIK, there's no privacy-respecting small provider offering server-side filtering rules.

[zimpenfish]

I suppose it depends on your definition of "privacy-respecting" and "server-side" but, for example, Proton offer SIEVE filters you can configure with a web UI.

https://proton.me/support/sieve-advanced-custom-filters

[nmjenkins]

Fastmail has way more powerful server-side filtering than either Exchange or Gmail. https://www.fastmail.help/hc/en-us/articles/1500000278122-Ma...

[sgtaylor5]

Fastmail does this too; their rules system is amazingly simple and powerful. Sieve rules too.