Can't send outgoing email

I have vista with Windows mail.  Norton internet Security 2010 is installed and updated.  It has just started not letting emails get sent out.  I receive incoming emails fine and if I turn off Norton scanning of outgoing emails they go out fine but I would like to have stuff scanned if I could.  Any help would be appreciated.   Almost forgot the error message that norton pops up is "unable to be sent because connection to your mail server was interrupted".  I don't get that if scanning is off. Thanks again for your help.