A note from isync's web site:

isync can be integrated into Mutt fairly easily with a few hooks:

	folder-hook ~A bind index $ <sync-mailbox>
	folder-hook +maildir 'macro index $ "<sync-mailbox>!mbsync the_channel:maildir\n"'

where the_channel is the Channel used to sync this mailbox, and maildir is the
name of the local mailbox itself. This works well so long as you are not
modifying the IMAP mailbox outside of Mutt. However, if you are using another
mail program simultaneously, Mutt will have the wrong idea of the local mailbox
flags and messages will start disappearing from its index display (don't worry,
they are still on disk).
