OneCare does not block email programs, particularly not Outlook, which is a known and trusted/signed program. I suspect that you have other security software still installed or partially installed that is causing this issue. If your prior security software was Symantec/Norton, for example, if the settings for their "smoke and mirrors" handling of scanning email means that your email is being routed through a proxy residing on the PC that is left there by Norton/Symantec. So, my advice is to remove other security software and run the removal tools provided by many vendors to insure that all components have been removed.
Norton Removal Tool - ftp://ftp.symantec.com/public/english_us_canada/removal_tools/Norton_Removal_Tool.exe
McAfee Removal Tool - http://www.majorgeeks.com/McAfee_Consumer_Product_Removal_Tool_d5420.html
If you continue to have a problem, please contact support.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve