Not really. As noted, ALL the headers to email can be faked and even if they are real,
all those Gmail, Hotmail, Yahoo Mail accounts come from the email server addresses, not the users who send the email.
If you are passing a system to someone else (selling or just giving), then you should
be sure to
delete all your personal data, delete all cookies and history, and change all account passwords using your new system.
delete all your personal data
There are two folders most people never see
XP: \Documents & Settings\Login-id\
Application Data\
Local Settings\
Vista & Win\7: \Users\Login-id\
Application Data\
Local Settings\
You may need to make these VISIBLE and then
delete ALL of the content.