Symptoms

K2 blackpearl cross domain/forest configuration. In a scenario where K2 blackpearl needs to interact with a SharePoint 2010 farm that is in a different domain and different forest, and the customer requires a one-way trust between SharePoint and K2, can this be achieved using K2 pass through authentication? Can it be achieved using Kerberos? Can K2 Support assist with the above authentication configuration?
 

Diagnoses

A one way trust might work with selective rights for the K2 Service account.
 

Resolution

We recommend to have a Two way trust between different domains or forests. Pass thru or Kerberos depends on how is your authentication set. K2 doesn't require Kerberos. If you have Kerberos set for sharepoint or in your environment then it is recommended to use it with K2. Here is a link on how to set different domains on for K2:

We follow the 1st approach to do add the domain thru Workspace and to modify the Worskpace web.config.
http://help.k2.com/onlinehelp/K2blackpearl/ICG/4.6.8/webframe.html_After_AddingMultipleDomains.html_tracksearch=Multiple Domain Configuration.