If you have opened some of these e-mails from people unknown to you, you may have picked up a virus. I'd suggest you do a virus scan with your antivirus program after updating it's definitions. If you do not have an AV program, you can do an online scan at TrendMicro.
I don't know of a way to stop the mailins, but suggest you delete ones that are unknown. And, I'd scan the ones that appear to be from trusted friends.
I don't know of a way to stop the mailins, but suggest you delete ones that are unknown. And, I'd scan the ones that appear to be from trusted friends.