[Dovecot] deleting maildir files

Greetings all...

Can we delete maildir files directly from the file system?

Basically, we use dovecot to train spam, and we want to delete messages that are older than 30 days, using a simple "find /maildirs -cname +30 -name *imap-server* -exec rm {} \;"

I have seen a post a while ago saying that dovecot can rebuild the indexes, but I don't remember if it's when the index is deleted or when the maildir files are deleted.

And if we cannot delete files with the 'rm' command, whats the best/proper way to delete these older files.

Thanks