We get this error 421.4.7.0 rainier.ispn.net error too many errors. I found a solution in the Norton Community to disable outgoing email scanning in Norton. I did this and everything was fine for a couple of weeks and then we received the same error yesterday. It only happens on one email that gets sent to a distribution list. We have Norton Internet Security and Outlook 2010. Is there anything else I can do to resolve this issue.