I am looking more or less for something like Google Wave, but still using the Standard protocols POP/IMAP/SMTP, so that it's still just Email under the hood.
I'd love to see the messages displayed as a thread, messages sent By me should be added to the threas (Not put aside in a folder called "Sent items".) and it would be nice if it could magically hide quoted prior messages and signatures.
As i am currenty using Thunderbird, an Addon would be great, but another Tool would be okay, too. (I am aware that TB offers a threaded view, but it doesn't meet any of the wishes I wrote above.) I'd be Happy to See suggestions, as my research on the Web did Not reveal anything so far.
EDIT: I am looking for a Desktop Client, as I Do Not want to be dependent on third Party Websites or Tools.