Have  to make a backup of e-mails in MS Outlook. That backup has to be
  readable by everything, so, ideally, a Maildir would be lovely.

  Now what?

  MS Outlook can only export  mails  to  "PST"  (a  useless  proprietary
  format) or CSV. Seriously, CSV.

  C-S-V.

  Not that we have standards like RFC822 or MIME... No, let's use CSV.

  Oh, dear.