When emailing from Smart Printing, there's currently no passive way to know if the document has failed to send. We have to hear that the email didn't make it, then go into the Sales Document Audit to see what happened. It would be better if there was a way to know that a Sales Document failed to email, such as a True/False box that could be used in a Workflow Rule, or maybe a Failure Queue/Notification Email.
Thank you for this idea! I've created an internal case for further review.