Created attachment 103699 [details] Stacktrace KMail showed the filter agent doing some job for ages in the statusbar, while emails came in unfiltered. When doing "akonadictl stop" in the process to reset things, drkonqi catched this crash, see attached backtrace.
This from the log might be interesting as well: org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_akonotes_resource' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_migration_agent' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_archivemail_agent' exited normally... Settings(0x22882e0) org.kde.pim.akonadicontrol: ProcessControl: Application "/usr/bin/akonadi_mailfilter_agent" stopped unexpectedly ( "Der Prozess ist abgestürzt" ) org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_mailfilter_agent' crashed. No restart! org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_newmailnotifier_agent' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_pop3_resource' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_birthdays_resource' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_indexing_agent' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_followupreminder_agent' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_maildispatcher_agent' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_notes_agent' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_vcard_resource' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_imap_resource' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_maildir_resource' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_sendlater_agent' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_contacts_resource' exited normally... org.kde.pim.akonadicontrol: Application '/usr/bin/akonadi_ical_resource' exited normally... KCrash: Application 'akonadiserver' crashing... KCrash: Attempting to start /usr/lib64/libexec/drkonqi from kdeinit sock_file=/run/user/1000/kdeinit5__0 QSocketNotifier: Invalid socket 31 and type 'Read', disabling... QSocketNotifier: Invalid socket 43 and type 'Read', disabling... QSocketNotifier: Invalid socket 48 and type 'Read', disabling... QSocketNotifier: Invalid socket 51 and type 'Read', disabling... QSocketNotifier: Invalid socket 53 and type 'Read', disabling... QSocketNotifier: Invalid socket 34 and type 'Read', disabling... QSocketNotifier: Invalid socket 49 and type 'Read', disabling... QSocketNotifier: Invalid socket 46 and type 'Read', disabling... QSocketNotifier: Invalid socket 52 and type 'Read', disabling... QSocketNotifier: Invalid socket 6 and type 'Read', disabling... QSocketNotifier: Invalid socket 24 and type 'Read', disabling... QSocketNotifier: Invalid socket 21 and type 'Read', disabling... QSocketNotifier: Invalid socket 167 and type 'Read', disabling... QMYSQLResult::cleanup: unable to free statement handle org.kde.pim.akonadiserver: Unknown exception caught in Connection for session "akonadi_mailfilter_agent" org.kde.pim.akonadicontrol: ProcessControl: Application "akonadiserver" stopped unexpectedly ( "Der Prozess ist abgestürzt" ) org.kde.pim.akonadicontrol: Application 'akonadiserver' crashed. No restart!
I'm experiencing the same bug. I'm happy to provide reports and do some testing, if this is helpful.
*** This bug has been marked as a duplicate of bug 374734 ***