OneCare does not block Outlook or the sending or receiving of email. This can happen, though, if you are using multiple security programs. If you turn off the OneCare firewall (change settings, firewall tab, disable) does the problem go away?
You may want to contact support -
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve