Donny Brooks put forth on 9/11/2010 2:14 AM:
We need this done asap as our backups are killing us with the large mbox style files.
Does your backup software not offer data deduplication? I was under the impression that all commercial backup software offered this feature in modern times. In a nutshell, if a file changes from one backup to the next, only the part of that file which has changed is then backed up, not the entire file. The "master" copy and the "fragments" are then merged during a restore.
If you don't have this feature, may I ask what backup solution you're using?
I'm not pointing you away from maildir. It is still preferable for some reasons in some environments. I'm simply saying, AFAIK, maildir simply doesn't have much advantage over mbox WRT modern (commercial) backup software.
-- Stan