Symptoms

SmartAction mails do not get processed any longer. Normally a K2Server restart fixes the issue, but we would like a more "long-term plan" to address this problem.
 

Diagnoses

With the old way SmartActions worked, we were dependent on Exchange EWSSyncState to keep track of which emails has been processed and which has not. Every now and then the EWSSyncState would get a little out of sync, and things would break. This caused the K2Server to stop processing the SmartActions mails. When you perform a K2Server restart, K2 would read the EWSSyncState column in the DB, and continue processing the SmartAction mail that was next in the queue. (This was the reason why a K2Server restart would normally fix this issue.)

Seeing as EWSSyncState is a little "error prone", we decided to move away from it and process the emails in the SmartActions inbox a little differently. Instead of relying on EWSSyncState, we now process the email in the inbox, and "move" them to the "Deleted" folder. This way, we know that all the emails in the inbox has not been processed and those in the "Deleted" folder has been processed. Now we no longer have to rely on EQWSSyncState. This is the way SmartActions are going to work in the future with blackpearl 4.7 and Appit 1.4 and onwards.
 

Resolution

We gave the client a "retro-fitted" coldfix based on the new way that SmartActions are going to work, and built on the 4.6.11 code base. The client applied the fix to their environment and it seems to have resolved the issue. The client said that I can go ahead and close the ticket.