Symptoms

SmartActions does not work the first time around. When we send a second approval mail, we get 2 responses back from the K2Server. One to state that is has been actioned and another stating the item can not be actionsed, because it HAS been actioned already.
 

Diagnoses

Looking at the K2Server email inbox, we noticed that the emails get sent to a "cluttered folder". Seeing as the K2Server looks at the inbox for smartaction related emails, we removed the "clutter" email from the equation and had the mails go directly to the inbox.
 

Resolution

After configuring the emails to go directly into the inbox instead of the "cluttered" folder, everything was working as expected.