http://wiki2.dovecot.org/HowTo/RefilterMail
That solution looks great for a single user, but is it possible to do a larger version that runs for everyone on the server? I'm speaking specifically of a virtual setup where all mailboxes are owned by a common UID/GID.
It seems like (with brief testing) that I could search for mail inside of a "Refilter" folder, like /var/vmail/domain.ext/username/Maildir/.Refilter/{cur|new}, and shove that through dovecot-lda.
I would just need to put the username/domain.ext back together in the format of username@domain.ext.
/usr/libexec/dovecot/dovecot-lda -e -d username@domain.ext -p (path to message)
If dovecot-lda doesn't throw an error, then I could delete the message from the "Refilter" folder and move onto the next message.
Or does Dovecot get horribly confused when messages vanish out of the "cur" folder?