In the process of moving to a new web server, I came across a small problem. On the old server, I'd been using Cryus for IMAP access. On the new server, to simplify things with Webmin/Virtualmin, I'm using IMAP-UW instead. It suits my purposes without overcomplicating matters like Cryus seemed to. The problem is that Cyrus uses a directory of email files and IMAP-UW uses one MBOX file with all the messages. I found several programs to convert from MBOX to Cyrus's format, but nothing to go the other way. After a lot of playing, I finally created something that works. And it works pretty well too.