Resolved: smtp.psu.edu intermittent errors
From approximately 3:26am through 5:31am a broken client caused some of the smtp.psu.edu servers to stop accepting new mail. The broken client was blocked and ITS is working with the client to resolve their issue.
Some users may have received an intermittent error of, “mail not sent”. No e-mail messages were lost and any queued messages from the affected servers were taken care of by the non-affected servers.
More information: Resolved: smtp.psu.edu intermittent errors
Story added 13. March 2014, content source with full text you can find at link above.