>> More ideas for e-mail clients
I'm kind of excited to note (with confidence) that Mozilla does actually store its labelling of messages on my IMAP server, as an "X-Keywords" header. (You can see this under the test folder here.) So I wonder how easy it is to do with XUL.
Assuming it's easy, I see all kinds of opportunities for mailbox organisation - things like being able to relate a message to any other message ("X-related: INBOX#message-id"), or a notation system ("X-related-note: nots#message-id"). Also global FOAF links, et al.
I'm also thinking of a mailbox-to-XML script to make things like that link above into friendly RDF feeds or something.