mb2md: convert mailbox to Maildir

The traditional Unix mailbox format -- often called "mbox" -- sucks. Maildir, a format invented by Dan Bernstein of qmail fame, sucks much, much less. Unfortunately, all the tools that I could find to convert mbox files to maildirs suck even more than the mbox format itself. (Eg. they do a bogus/incomplete conversion and then delete the input mbox without warning -- that sort of thing.)

So I wrote my own mbox-to-maildir conversion tool, called mb2md (all the obvious names were taken). Bragging points:

• mb2md does not destroy your valuable email. It insists that the output maildir not exist when you start, so you know that the output maildir exactly matches the input mbox. More importantly, it does not remove the input mbox when finished -- so if you decide you don't like what mb2md did, you can fallback to your old mbox.
• mb2md (or rather, the addtomaildir script that does the real work) takes considerable pains to preserve all useful information from your mbox file. Specifically, new/old/read messages in the mbox remain new/old/read in the maildir. Also, it attempts to figure out the delivery time of each message in the mbox, and sets the mtime of the corresponding message file in the maildir from it -- that way, you can easily sort the maildir by delivery time.

Requirements/download

• an external tool to split the input mbox; currently, either one of the following will work:
  • formail (supplied with procmail)
  • reformail (supplied with maildrop)
• my addtomaildir script, which does the real work of analyzing each message from the mbox and adding it to the maildir (requires Python 2.2 or greater)
• the mb2md shell script itself

chmod +x mb2md addtomaildir

Acknowledgements

Thanks to the following people for patches and so forth:

• Roman Neuhauser (neuhauser at bellavista dot cz)
  (made it work with reformail in addition to formail)
• Freek Dijkstra (freek at macfreek dot nl)
  (tweaked "From " regex in addtomaildir to support Postfix)
• Steven Davis (sgdavis at bioneos dot com)
  (suggested a fix for the "addtomaildir runs as shell script" problem described below)

Share and enjoy!

Alternatives

A couple of people have reported a peculiar problem with mb2md: when formail runs addtomaildir, it runs it as a shell script, not as a Python script. Unsurprisingly, this does not work very well. (Yes, in both cases I told the person to make sure addtomaildir was executable, and in both cases it was.) Unfortunately, since I don't maintain mb2md at all (it's a one-off tool: convert your mailboxes and you're done with it), I have no time to investigate. But there's an alternative: Juri Haberland's mb2md.pl . Give it a try.