Within a workflow that I was developing, there was a requirement to notify a group of SharePoint users that a lookup service had failed. This particular activity was within a parallel activity sequence. I chose to use the SendEmail activity to notify the users, but incorrectly set the Correlation Token to a new value. When testing this functionality in the workflow I received an error:
The correct Correlation Token for a SendMail Activity is the “Workflow” token. The reason, which is fairly obvious, is that the SendEmail activity maps to the workflow, not to a task, which would require a Task Token.