Someone sent spam email purportedly from me to everyone on my contact list. How can I prevent this from happening again?

Hello, it seems someone has hacked your mail account, this may be as a result of malware or spyware on your computer or while surfing a non-secure website. To prevent this:

1. Log into your account and change your password and answers to your security questions, use something stronger this time.
2. Never tell your browser to remember your passwords.
3. Never click on any links in your emails, instead copy the link, open a new tab on you browser and paste the link in the address bar.

All the best, thanks for using FixYa

Perform an immediate virus scan, your computer may be infected. Hackers get in through malicious links you may have clicked, and this is what results from those hacks.

Also perform malware and spyware scans, either of these can cause an issue such as this as well.

Change your password frequently, make it difficult so a hacker cannot gain access to your account.

Be sure to change your password after performing these scans, otherwise anything on your computer that a hacker will have, they will still have if you change your password prior to the scan.