[Dovecot] How to know when a mail is moved from a folder to another

Hi all,

somebody know how to know when a mail is moved from a folder to
another ?

My goal :

Each imap mail account have at least a folder named 'Spam' where all
mail tagged spam by spamassassin are going.

I've a script who check if a non-spam tagged mail is added to this
folder by a user to permit to spamassassin to learn it as spam. There are few mail in spam folder, so this solution is good for me.

In the same idea, I want to know if a mail is moved from spam folder
to another folder to permit to spamassassin to learn moved mail as
non-spam. Cause all mailbox have more than ten thousand of mail, I can't use
the same system.

If anyone have an idea ...

Thanks,

Cyril Feraudet