I have a workflow built in SPD 2010 that is set to email a user if a condition is met. The workflow shows completed, but the email does not send and gives the error message in my question.
Here is the strange thing. It worked once. Then it started failing and giving the error message.
I decided to leave it for the day and go on to some other issues. When I came back to it this morning, I created a test item in my SP list to start the workflow. The workflow completed and sent the email, which I received. Subsequent attempts to recreate this success have been, well, unsuccessful. The workflow completes, but the email does not send and the same error message logs.
Why would it work once and then fail in subsequent attempts?
Other emails are successfully sending from other workflows and System Account is the sender, so I wouldn't think that was the issue.