Due to whatever I had all my folders in "Local folders" duplicated, i.e. (translated to German) two outbox, two trash, two drafts etc. Once of these pairs I could delete, for the other the "delete folder" was disabled in the context menu. After I deleted the folders and only had one each left I opened the online imap's account settings to check which trash folder it uses. It used "trash" which does not exist. So I opened the "select folder" dialogue to pick the proper trash folder, i.e. "Mülleimer". As you can see the dialogue lists outbox and "Hochzeit" (some custom folder) twice although akonadi does not have them twice in its browser. restarting akonadi + kmail2 did not change the situation. Reproducible: Always
Created attachment 72964 [details] duplicate folders showing up in kmail's "select folder" dialogue while akonadi does not list them twice
Created attachment 75459 [details] Screenshot showing the double trash in the choose collection config dialog On my install there are just two local trash folders and they are only displayed in kmails choose collection config dialog, not in the folder list. So this might either be unconnected or the bug has been halfway fixed in the meantime. (aside: Interestingly, my inbox is called "Posteingang" in the file system, but "inbox" both in Akonadi and kmail. Surely, this is because I installed in German and later switched the application language to English for bug reporting reasons. But I'm a bit surprised that the Akonadi console doesn't show the real file system name. Plus, it's weird that the German file system name is translated back to English.)
This bug has only been reported for versions before 4.14, which have been unsupported for at least two years now. Can anyone tell if this bug still present? If noone confirms this bug for a Framework-based version of kmail2 (version 5.0 or later, as part of KDE Applications 15.12 or later), it gets closed in about three months.
Just as announced in my last comment, I close this bug. If you encounter it again in a recent version (at least 5.0 aka 15.08), please open a new one unless it already exists. Thank you for all your input.