maildir2mbox - move mail from a maildir to an mbox
maildir2mbox moves mail from a maildir-format directory to
an mbox-format file.
You must supply three environment variables to
maildir2mbox: MAILDIR is the name of your maildir direc-
tory; MAIL is the name of your mbox file; and MAILTMP is a
temporary file that maildir2mbox can overwrite. MAILTMP
and MAIL must be on the same filesystem.
maildir2mbox is reliable: it will not remove messages from
MAILDIR until the messages have been successfully appended