While I gave up local mails and subordinated entirely to google meanwhile, my partner still wants to be independant and prefers local mails. Since KMail seemst to be wrecked, I have to migrate her mails to the old mbox format of thunderbird. This one-command-recipe worked for me. I replaced Archive/ by e.g. .kde/share/apps/kmail/mail/inbox and sarchive by sMBOXinbox . To import MBOXinbox they simply have to be copied to ~/.thunderbird/.....default/Mail/Local\ Folders . Converting Maildir to mbox via mutt Ran into an issue today where I needed to convert a Maildir containing over 50k messages to mbox format and couldn’t really find any good tools. So I found this blog post about using mutt to do it. Unfortunately, it converted one Maildir to another. =( One crucial piece is missing, so here is the one-liner in all its glory: $ mutt -f Archive/ -e 'set mbox_type=mbox; set confirmcreate=no; \ set delete=no; push "T.* ;sarchive "' The above convert...