Workflow Task Email escalation causes "The parameter 'addresses' cannot be an empty string" error


Workflow Task Email escalation causes "The parameter 'addresses' cannot be an empty string"error

This article was created in response to a support issue logged with K2. The content may include typographical errors and may be revised at any time without notice. This article is not considered official documentation for K2 software and is provided "as is" with no warranties.


A K2 Workflow Instance goes into error state when an Email Escalation is executed with an error message:
"The parameter 'addresses' cannot be an empty string. Parameter name: addresses"



The issue will be encountered when a Workflow Task Recipient is set to a K2 Role and an Email Escalation is also configured to execute after a specified Time with "Send email to task participants" selected. 


When the Email Escalation is triggered, the Workflow Instance will go into an error state.


The error is expected due to the way the Workflow is configured.

Because the Task is assigned to a K2 Role and it has not been opened yet, there is no individual users associated with the Task. When the Email Escalation is triggered, no users and therefore no email addresses are available to send the email to, causing the error. 

Should Email Escalation be required on a Task assigned to a K2 Role, the "Resolve groups to individuals" option needs to be enabled on the Task Result Rule Tab under the Options section.




This will create a Task for the individual members of the K2 Role instead of the K2 Role directly. When an Email Escalation occurs, the mail will be sent to the specific user(s).

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This Solution is not working

There can be many scenarios to get that type of error. I would suggest logging a Nintex Support case.


Things like From Address is empty, one of the destinations resolves to empty email address which will all depend on workflow design to know where the issue lies. 




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