We tried, but could not find /doku.php?id=doku.php.faq:favoriteclient:i_have_duplicate_mails_in_my_sent_items_folder._why&do=login§ok=02caa76c1f08d21c6cdbf4413a687c2a
But hey, you don't have to leave empty handed!
Here are some things you can try instead: