Task notifications fail to send out with the following error shown in the K2 Host Server logs:
"Error","EventBus","7498","General","MSMQ.RecieveMessage","7498 An error has occurred: Item:0 - System.Messaging.MessageQueueException (0x80004005): Operation was cancelled before it could be completed.
at System.Messaging.MessageQueue.ReceiveCurrent(TimeSpan timeout, Int32 action, CursorHandle cursor, MessagePropertyFilter filter, MessageQueueTransaction internalTransaction, MessageQueueTransactionType transactionType) at System.Messaging.MessageQueue.Receive(MessageQueueTransaction transaction) at SourceCode.EventBus.MSMQSource.MessagesFromSource.RecieveMessage()"
Email messages are stuck in the MSMQ queue. To confirm this, go to Administrative Tools > Computer Management > Services and Applications > Message Queuing > Public Queues > eventbus > Queue messages.
Restarting the 'K2 Blackpearl Server' and 'Message Queuing' Services allow messages in the Queue to clear and task notifications to be sent out. However, more messages continue to get stuck.
To resolve this, configure K2 to use Private Queues instead. Please follow the guidelines in this KB article: http://help.k2.com/kb000198