Openwebui has a lot of functionality like custom plugins, filters, pipelines and whatnot.

What are you looking to enhance and what do you feel like you are missing there?

I have tried kmail, Geary, mailspring before I landed on betterbird. I’m not sure what you mean with slow, but it works without issues on my pc. It does a lot of stuff, but it’s a fork of Thunderbird, which you want to exclude based on the initial thread. There are not a lot of linux clients even worth trying. Good luck finding your jam.

That is an easy way to make less traffic from people that don’t really care. When I see it, I close the page and look for the next result.

If you really need to know what is written there I guess you can Log in or use redlib or something like that.