With Neon User on my laptop and desktop: kmail accesses via imap and dovecot server the same account. Both kmail instances have only the 4 bogofilter rules generated by the antispam wizard.
When both kmail instances are running and I receive a new e-mail, the same e-mail is listed multiple times in the msg listview and akonadi scans the inbox again and again. Each scan ~ 4 sec and CPU fan kicks in because akonadi consumes lot of CPU. The scan loop stops after more than one or two duzend scans (guess). The mesg list view shows 2 times the same unread msg. This happens on both the laptop and desktop in parallel.
After each scan the msg switches most of the time between listed twice and four time. Sometimes it's listed 3 times. When it eventually after 1 -2 minutes ends I see the new msg listed twice.
At the same time the unread mail count changes again and again in kmail/inbox,
thunderbold, K9-Mailon Android and Apple Mail and I can enjoy lots of notification sounds ;-)
When I disable the all rules (=4 bogofilter rules) on the laptop. I don't see the duplicates but nevertheless my laptop does one complete sync the inbox as shown in the msgbox in the lower right of kmail which takes ~ 4 sec.
I've seen this in the past already (> year) but most of the time I used
bogofilter filter rules only on the desktop host.
I can end the endless loop, when I mark all listed entries of the msg as unread
Created attachment 111132 [details]
xsession error of the sync loop
This time the sync was ended by 2 new msgs arriving, tickering akonadi into a full reload of the inbox (~ 4 min instead of ~ 4 sec for the normal syncing)
The 'BAD Error in IMAP' occur when the regular backgroud check of the folders of my T-Online account happens. (fraction of sec for each folder).
This affects me also.
Uninstalling Bogofilter stopped the duplicate behaviour in Kmail - and all other devices. eg Fariemail on Android.