I am still convinced that it is not Symantec.  Do you have a spare computer we can test on?
If you do have a test computer, I would install Netscape, configure your email then test sending email.  
Here is a permanent solution:  If your email is pop email, hosted exchange etc, you could use Microsoft Outlook.  If you use Outlook, 110% you will have a history of your sent items.
I tried booth and nothing