you mean your friends recieve spam emails from your account but you never sent it , then it means your account got hacked or something.
One should always have a personal e-mail account which is not shared anywhere else... except friends and family and important business. This way, you would remain trouble-free, most of the times. Regards, RightMan
I beleive that's because you have supplied your yahoo e-mail address at more places than your gmail e-mail. I agree with Rightman, that you should have a personal e-mail that you don't provide to any sites or newsletters. You can share it with family,friends and important sites with no spam e-mails so you can be spam-free Best regards, Adel