KMail: “Multiple Merge Candidates” error and how to fix it


If you can’t synchronize a folder in KMail and you are seeing “Multiple Merge Candidates” error after the synchronization fails, here’s a how to fix the folder to make it synchronize again – basically you force KMail to forget and re-sync the folder again.


  1. Open Akonadi Console.
  2. Go to the Browser tab.
  3. Right-click the broken folder and select “Clear Akonadi Cache” – this will remove all emails from the folder in Akonadi. This will NOT delete your emails on the server.
  4. Akonadi Console will freeze for a while, wait until it unfreezes (sorry, it’s just a developer tool, we don’t have a very good UX there :-)).
  5. Logout and login to make sure all PIM components are restarted.


After login start KMail (or Kontact) and hit “Check mail“. KMail will now re-download all emails from the previously broken folder. This may take a while depending on how large the folder is and how fast your internet connection is. After that the synchronization should work as expected.


In the upcoming KDE Applications 16.12.1 release Akonadi will have a fix that fixes the reason why the “Multiple Merge Candidates” error occurs, so hopefully in the future you should not see this error anymore.

15 thoughts on “KMail: “Multiple Merge Candidates” error and how to fix it

  1. jkt

    Is there a reason or a use case why this action has to be performed by the user? Why not do it automatically?

    • First, it’s not always a bug when RID is duplicated, it won’t break all the resources – it basically only affects IMAP/Kolab, so automatic detection would not be 100%. Second, because I don’t want Akonadi to suddenly decide to start re-downloading your massive folder when you are on mobile internet or something.

  2. I have to often clear cache because KMail goes out of sync when you check mails on multiple devices. This would be a good option to implement in KMail UI itself.

  3. lord rel

    any chance for some love for bugs that are really old and still a problem? the 293918 duplication bug is almost 5 years old and the 118213 bug is 12 years old

  4. Félim Whiteley

    Thanks for your work on KMail, it is VERY much appreciated!

    Is there any way to reindex the “Local Folders” ones also? I’ve used one to drag some IMAP mail that was important but didn’t need to be on the server. I had some issue and the index files got mangled and not the folder appears empty from the point before that.

      • Vojtěch

        This doesn’t work for me. :-( I was moving to new computer and I copied ~./local/share/local mail to new computer and set up all Akonadi resources. And I’m keeping having this error. The described trick does nothing. Commonly it happens that I click on local e-mail and I see just information that its content is loading, but it never happens. I must restart Akonadi. Local Folders resource is also commonly reporting it can’t connect to Akonadi.

  5. Thomas

    Thanks for your work on kmail / akonadi. Really, it _is_ appreciated!

    please: where to find information about the current status regarding?:

    1) printing of mails (currently it opens external browser to print, which is kinda “unfunctional”)

    2) drag and drop of mail attachments is not working. Instead of the file, it adds the reference to the text of the mail (e.g. “attachment:2?place=header”)

  6. Fulano

    A humble request: Could you write a status update on what’s going on akonadi and akonadi-next?

    • In short: Akonadi-Next is now called “Sink” and is being worked on by Christian Mollekopf and others from Kolab Systems, I’m not involved in the development at all, so can’t really give any update on the state of Sink or Kube (their email client built on top of Sink).

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