Can not send emails to Hotmail accounts when I Turn on Scan Outgoing Email

Hello all,  I just found out the following issues with my mercury mail server. I notices that hotmail account can never receive any emails from my mail server. however, Hotmail account can receive emails from my mail server if I trun off "scan outgoiing email" in Norton Internet Security. one more note, this only affect hotmail accounts. I have no ideas about what is going on. I never get any error message when Norton delete these emails.  However, I still want to have "Scan outgoing email" feature or have miniminal protection for my mercury mail server. please advise?  thank you in advance!