How to stop spams which send mails by them self from my gmail ID?
Yesterday i encountered a problem where I realized that, All my friends in my contact had got a email from my gmail id that had a link in it. I had not sent any such email. It was a spam email that got sent by itself. Is there a way to stop such actions in future so that I do not send emails to all my contact without my knowledge.

I use Gmail. Please let me know your suggestions. Thank you for your time and advice. 
How to stop spams which send mails by them self from my gmail ID?
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Yesterday i encountered a problem where I realized that, All my friends in my contact had got a email from my gmail id that had a link in it. I had not sent any such email. It was a spam email that got sent by itself. Is there a way to stop such actions in future so that I do not send emails to all my contact without my knowledge.

I use Gmail. Please let me know your suggestions. Thank you for your time and advice. 