[Dovecot] make archive emails undeletable?

I've been using dovecot for a year or two now, and really like it. I have a fairly simple setup, but I think it's time to get a little more advanced. I keep an "archive" of all my email, both sent and received. Every once in a while I get confused, and accidentally delete something from my archive. I also worry that I'll misconfigure a mail client some day and accidentally wipe out my "trash" folder. I would like some way to prevent deletion in several mailboxes. Is that possible? It looks like ACL could do this, but I can't quite figure out where to start. Any pointers would be greatly appreciated.

Thanks, Rob