Flashing authentication failure

I'm running the latest version of KDE Neon with all updates.
I currently cant use Kontact because Kmail detects an authentication 
failure and keeps repeating an authentication failure message at a very 
rapid rate

The only way I've been able to control  this behaviour is issuing 
akonadi stop.
An extract from the logs is below

Any thoughts on how to fix this would be much appreciated

Tony


2024-06-29T16:45:13 [INFO ] org.kde.pim.akonadiserver: 
./src/server/storage/itemretrievalmanager.cpp:181: void 
Akonadi::Server::ItemRetrievalManager::retrievalJobFinished(Akonadi::Server::A
bstractItemRetrievalJob*): ItemRetrievalJob for request 627 finished
2024-06-29T16:45:13 [INFO ] org.kde.pim.akonadiserver: 
./src/server/storage/itemretrievalmanager.cpp:181: void 
Akonadi::Server::ItemRetrievalManager::retrievalJobFinished(Akonadi::Server::A
bstractItemRetrievalJob*): ItemRetrievalJob for request 628 finished
2024-06-29T16:45:18 [INFO ] org.kde.pim.akonadiserver: 
./src/server/storage/itemretrievalmanager.cpp:181: void 
Akonadi::Server::ItemRetrievalManager::retrievalJobFinished(Akonadi::Server::A
bstractItemRetrievalJob*): ItemRetrievalJob for request 629 finished
2024-06-29T16:45:19 [INFO ] org.kde.pim.akonadiserver: 
./src/server/storage/itemretrievalmanager.cpp:181: void 
Akonadi::Server::ItemRetrievalManager::retrievalJobFinished(Akonadi::Server::A
bstractItemRetrievalJob*): ItemRetrievalJob for request 630 finished