A Perl script that takes one or more Mbox format mailbox files in a directory and convert them to Maildir format mailboxes. As the Mbox format has some drawbacks, D. J. Bernstein created the Maildir format when he wrote Qmail. With the Mbox format all mail of a specific folder is stored as one large text file. The Maildir format stores each mail as a separate file. It is a faster and more efficient way to store mail. It works particularly well over NFS, which has a long history of locking-related woes. The Mbox format is used by most of the POP3/IMAP servers, most mail servers (MTAs) and mail readers (MUAs). The Maildir format is used by Qmail, Courier-MTA and can be also used as a alternative mail storage format by Postfix and Exim. A good POP3/IMAP server for Maildirs is Courier IMAP.
Mb2md.pl does not only convert mailbox files into a Maildir but also the /var/spool/mail/$USER mailspool file. It is smart enough to not transfer a dummy message such as the UW IMAPD puts at the start of Mbox mailboxes - and you could add your own search terms into the script to make it ignore other forms of dummy first message.