An emptier mailbox

I was pretty happy to have 18,000 mails in my inbox. Because I use search to find what I need instead of folders.

Unfortunately I just realised it's slowing down operations, e.g. when I start mail it tries to sync my work and offline copies of the mailbox, which takes a long time.

So I've deleted all mails from 2006 to 2008, leaving me only 3,000 there.

I'm sad about this, because the bad design of the software means I have to have the mailboxes organised a different way to what I want.