What is best alternative to Windows Live & Outlook 2010 that works with Norton Internet Security?

Currently we are looking for alternatives to Outlook 2010 and I tried Thunderbird as an open source and free email pkg and everything was working great until I installed Norton Internet Security 2011 and the email scanning would not work and is not supported by Norton.

 

I am not a fan of web mail as I often need to access my mail folders while not connected to the Internet. So Windows Live and other web mail apps do not meet this requirement.

 

I am looking for an email app that is supported by Norton 360.  Any suggestions would be greatly appreciated.

Thanks

 

KLThor