For the last four days, I had been using my other machine. When I came back to this one and ran KMail, it first said that Akonadi was not operational, so I closed KMail, ran `akonadictl stop` then `akonadictl start`, and ran KMail again. I then noticed that a few e-mails, that I had read on the other machine (but were new to this one), had been duplicated 36 times (but without their bodies) into three of my other accounts (two were spared). Then, DrKonqi informed me that the IMAP resource corresponding to the “source” account had crashed. Unfortunately, I don’t know what triggered this bug and thus cannot reproduce it. (Nor do I really want to…) Reproducible: Didn't try
Created attachment 92667 [details] one of the original e-mails
Created attachment 92668 [details] one of its copies
Apparently, the two accounts that I thought were spared (my @free.fr addresses) were in fact not. Copies are visible from the webmail provided by Free, even if not from KMail.
I have a very similar bug for a few days now. No and then akonadi/kmail2 seems to duplicate messages, but the duplicates are greyed out "dummies". The only possibility to remove them is to go to the webmail interface and delete the duplicates there.
Maybe the bug is related to this one: https://bugs.kde.org/show_bug.cgi?id=348103?
This one does look like a duplicate, indeed. My bad. *** This bug has been marked as a duplicate of bug 348103 ***