Converting Mbox mailboxes to Maildir format

Overview

Maildir is a structure for directories of incoming mail messages that solves the reliability problems that plague mbox files. A directory in maildir format has three subdirectories, all on the same filesystem: tmp, new, and cur.

Each file in new is a newly delivered mail message. Files in cur are just like files in new. The big difference is that files in cur are no longer new mail: they have been seen by the user's mail-reading program. The tmp directory is used to ensure reliable delivery. For a new user who does not have existing mail messages in mbox format, all that is required is to create the ~/Maildir directory and its tmp, new, and cur subdirectories all owned by the user.

The mb2md conversion script

For an existing user who has existing mail messages in mbox format, the mb2md script is useful for converting the existing messages to maildir format.

Reference: Converting Mbox mailboxes to Maildir format