Kmail Version 5.17.3 (21.04.3)
Kmail no longer displays e-mail message text. Header details like Subject, Date, From and To are there but no message text.
Kmail also no longer retrieves new messages.
A possible clue are akonadiserver errors I can see:
[xxx@yyy ~]$ akonadictl restart
org.kde.pim.akonadictl: Starting Akonadi Server...
org.kde.pim.akonadictl: done.
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
[xxx@yyy ~]$ org.kde.pim.akonadiserver: Starting up the Akonadi Server...
akonadi.collectionattributetable OK
akonadi.collectionmimetyperelation OK
akonadi.collectionpimitemrelation OK
akonadi.collectiontable OK
akonadi.flagtable OK
akonadi.mimetypetable OK
akonadi.parttable OK
akonadi.parttypetable OK
akonadi.pimitemflagrelation OK
akonadi.pimitemtable OK
akonadi.pimitemtagrelation OK
akonadi.relationtable OK
akonadi.relationtypetable OK
akonadi.resourcetable OK
akonadi.schemaversiontable OK
akonadi.tagattributetable OK
akonadi.tagremoteidresourcerelationtable OK
akonadi.tagtable OK
akonadi.tagtypetable OK
org.kde.pim.akonadiserver: Running DB initializer
org.kde.pim.akonadiserver: DB initializer done
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
org.kde.pim.akonadicontrol: Akonadi server is now operational.
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7fbf6c003f20) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7fbf6c0104e0) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7fbf6c003f20) identified as "ETMCalendarMonitor - 94644443239184"
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7fbf6c0613a0) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7fbf6c014010) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7fbf6c015b80) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7fbf6c015040) )
org.kde.pim.akonadiserver: DATABASE ERROR:
org.kde.pim.akonadiserver: Error code: "1292"
org.kde.pim.akonadiserver: DB error: "Incorrect datetime value: '2021-08-08T16:44:49Z' for column `akonadi`.`pimitemtable`.`atime` at row 1"
org.kde.pim.akonadiserver: Error text: "Incorrect datetime value: '2021-08-08T16:44:49Z' for column `akonadi`.`pimitemtable`.`atime` at row 1 QMYSQL: Unable to execute query"