“I had installed Windows 10 a few weeks back all looked fine until I had to send an email via outlook, I can send emails but, I have lost my calendar and all contact lists. Missing Outlook contacts is one major issue for MS Outlook users who have upgraded to Windows 10. Windows 10 is increasingly becoming popular among users, upgrading to Windows 10 is easy, however, at times upgrades can trigger major or minor data loss. Summary: Microsoft releases regular updates of the Windows operating systems to enhance new features and to fix security patches.