maildir_merge_duplicates.py Removes duplicate emails/files in a Maildir and merges their flags. Duplicate emails in a Maildir can occur e.g. when restoring a backup. Maildir stores its email flags in the filename itself. If an email status changes from unread to read a ",S" is appended to the end of the filename. Imagine now that something bad happened with your Maildir and some mails got lost/deleted, but you don't know which ones. In a normal restore scenario you would instruct your backup software to not overwrite existing files to make sure that you don't destroy the changes on other files done since the last backup. In this case you will end up with lots of duplicate emails in the case that the flags changed from the time of last backup. In fact you have overwritten existing information - the messages status flags. Another source of Maildir clutter might be a sync software that doesn't handle the specifics of Maildirs. In either case you want to delete the duplicate mails but you don't want to delete the "wrong" mails with the outdated flag information. maildir_merge_duplicates.py cannot magically know the original and the duplicate message of course, but it can merge the flags of the duplicates and delete the other message for you.