Norton Secure VPN blocking sent mail in Windows Live Mail 2011

Email providers often block VPN's because they see you accessing your account from a different location than they expect to see you. In case it is someone trying to hack your account, they restrict access. 

Are you using the web based access to your Live Mail, or are you using a local email client such as Outlook or Thunderbird?

If using the web based access, contact support for Live Mail and see if they have any work around for using a VPN.

If a local client you can add the email client's .exe file to the Split Tunnel feature of the Norton VPN feature. From the new My Norton interface click on the down arrow beside Turn on/off beside the VPN feature, then click on Settings. Click on Split Tunnel and then click add. Find the exe for the client and add it. Then you should not have any issues with your email as it will bypass the VPN.