Invoke procmail on spool file using new .procmailrc?

I've recently configured new .procmailrc and .forward files to work with our Postfix mail server. I've tested it with new Emails, and the new .procmailrc is properly filtering and forwarding as desired. Now I would like to somehow re-process the entire contents of my /var/spool/mail/***username*** file using the new .procmailrc so that all 2000+ messages will be properly sorted into my new ~/mail/Likely-Spam, ~/mail/Almost-Certainly-Spam, ~/mail/Cron-Jobs, ~/mail/Email-Backup, etc..., and forward all non-filtered messages to my company outlook account... for posterity. Is there a straightforward command to accomplish this? My mail server is running RHEL 7 with postfix.