Symptoms

Notifications aren't being sent out
 

Diagnoses

Client event task notification is not sending email event is working. The following error is logged:

"3060603","2015-05-04 21:15:37","Error","MessageBus","61007","SendMessageException","MessageBusRuntime","61007 Permanent failure sending message New Task: System.Exception: No destinations could send the message New Task.
at SourceCode.MessageBus.Server.MessageBusRuntime.SourceCode.MessageBus.IMessageDestination.Send(String title, MessageExtendedInformation extended, IEnumerable`1 attachments, MessageBodyReadere] messageBodies)","","","CP-K2DEV:C:Program Files (x86)K2 blackpearlHost ServerBin","3060603","4fcc91b39d72471fb53f6ca44a46bec0",""

Using Exchange online/Office365.
 

Resolution

K2 Smartactions was enabled, as such the "self" node in the K2Hostserver.exe.config file will be used to determine the email address and which available EWS connection string to use:

<system self="K2:DENALLIXK2Service" enableListeners="True" allowAmbiguity="true" />

Executing the UMUser Smartobject > Get User Details against the specified "self" account did not return an email address. As such we updated this account's email address in AD, expired the account's identity cache using the Force Identity Refresh Tool, re-cached the account's detail by executing the UMUser Smartobject > Get User Details Smartobject again. Task notification is now sending correctly.