Outlook starts sending spam emails to contacts issue generally occurs due to virus or malware attacks that leads to hacking of your outlook account. You can resolve this issue by changing your outlook password on temporarily basis. Just in case if you fail to fix this issue, then you need to contact Outlook Support instantly. Another solution you can also try to resolve this issue is through scanning hard disk of your computer with advanced antivirus software. At the same time, you also need to inform your email contacts about the issue, so that they simply ignore the emails from your email address.