Dovecot default email order

How to change it, if it matters

For some programs it might matter, in which order LIST IMAP command shows emails by default. For example, it might be the reason behind Issue 726 for K-9 Mail. Or, at lest, it was for me.

To fix it in dovecot IMAP server while using maildirs, you can do the following: move all mails to a hidden directory and copy them back one-by-one, issuing doveadm index command after each mail.

These are the commands:

sudo service dovecot stop     # stop dovecot server to prevent influence
cd ~/Maildir                  # cd to a target folder
rm -f dovecot*                # remove all dovecot indexes
mkdir hid                     # make hidden directory
mv cur/‌* hid/                 # move all mails there
for file in $(ls -rt hid); do # walk through all mails, starting with oldest one
    mv hid/$file cur/         # move a file back
    doveadm index INDEX       # rebuild dovecot index
done
rmdir hid                     # remove temporary directory
sudo service dovecot start    # start dovecot server

Note that you can do it for any IMAP folder, just change ~/Maildir and INDEX to paths to the same folder in filesystem and on IMAP server.