Symptoms

The workflow fails while trying to send a notification with the error "SourceCode.Workflow.Common.EWS: The e-mail address does not have ‘send on behalf of’ permissions on Exchange"
 

Diagnoses

This is a known issue when using a SmartActions account that is different from the K2 Service account.
 

Resolution

Grant "Send As" permissions to the From account for the K2 Service account