Edit: I just found the great Gmail Lab “Advanced IMAP Controls” which will let you select which mailboxes to show in IMAP. I would say that is probably a better alternative.
There have been many posts about this on other blogs: why does everything in inbox also appear in All Mail? Ugh that is so annoying
Anyway, here is what I did so that would not bug me:
Follow the directions here, and it should be nice and working
But then a few minutes later you say “wait… when I send mail from any other client (like my android phone or the gmail web interface) it doesn’t go into that IMAP/Sent folder!”
Solution: apply a filter
Add a filter in gmail’s web interface that filters all mail that is from (your-username)@gmail.com and applies the filter IMAP/Sent (see this screenshot)
Now it works! Gmail should really put something like this on their instructions for setting up Mail.app
