There are already tools to convert from Microsoft Outlook and Outlook Express's proprietary mail database files to Unix mbox format (0, 1, 2, 3). But Outlook can also export a mailbox in 'text' format, which looks a bit similar to mbox but is not the same, or in CSV format. This is a pair of tools to convert these two formats to standard mbox. It is not the recommended way to get mail out of Outlook (try setting up a second account using IMAP and transferring messages to that), but it's useful if the text or CSV files are all you have.
All the files are in the public domain. This means there are no copyright restrictions, you may do what you wish with them. Of course, giving credit would be appreciated (but not required).
They are offered as-is with no warranty whatsoever.
Please contact me, Ed Avis <firstname.lastname@example.org> with any suggestions or bug reports. I would like to extend this program to cope with other 'doomed to reinvent it, poorly' mbox-like formats, provided they are fairly similar to Outlook's.
This program has a web page at http://membled.com/work/apps/outlook_text_to_mbox/.