So, you’ve realized your email address is sending out spam. How did this happen?
Somehow, maybe through email spam yourself, you installed malicious software that sent your email credentials to a spammer. Either that or it is an automated spam system where if you install a program from a spam message, it will automatically send spam to all your contacts.
The best way to avoid this? Don’t install programs from email messages. Also, it might be a good idea to invest in something like Zonealarm. Zonealarm can prevent malicious software from gathering the information required to send out spam if you look at the prompts.
At this point, if your email address is sending out spam, it’s a good idea to back up all your data and reinstall windows. That’s your best solution, and be more careful in the future by using Zonealarm or something similar, like kaspersky, avg and others.