After some years of succesful performance, messages to me from my sister's Outlook 2010 (W7) via Comcast fail to arrive both at Earthlink's server and thus into my Outlook 2007 (XP). Messages she sends from Comcast's webmail site arrive normally. Messages that she sends to one other known Earthlink user also fail to arrive. All other two way message traffic from her Outlook behaves normally. I installed a second account for her on my 2007 Outlook and it behaves normally even sending to myself. Both e-mail service providers claim innocence. All this seems to implicate her Outlook installation. She ran the Office 2010 repair routine to no effect. What do you recommend to further diagnose and solve this issue including I suspect the reinstallation of Office 2010?