How to Archive and Backup Emails with Postfix and Dovecot Subfolders on Ubuntu Servers

I've been thinking recently that as well as an off-site compressed backup of all of the emails within my system, I would also like a (relatively) easy way to recover an email that one of my users has accidentally deleted from their their trash folder (i.e. it's gone forever).

So how do we archive and backup emails with Dovecot? It's actually quite simple, and if I say so myself.. clever :-)

Step One:

Blind Carbon Copy, always_bcc