MICROSOFT OUTLOOK EMAIL PROBLEM

MY MICROSOFT OUTLOOK HAS RECEIVED REPEATED EMAILS FROM THE SAME SENDER EVERYDAY, IS MY PC GETTING VIRUS INFECTED OR THE SENDERS' PC GETTING VIRUS INFECTED? WHAT ACTION SHOULD I DO, THERE ARE SEVERAL PCS CONNECTED TO THE EMAIL SEVER, BUT THOSE CC RECEIPIENTS HAS NOT RECEIVE REPEATED EMAIL AS COMPARE WITH THE ORIGINAL RECEIPIENT. WE ARE USING FIREWALL AND ANTI-VIRUS SOFTWARE ALREADY.