You can block users if you do not want to receive their communications; additionally, you can report a concern to Microsoft. Notice to non-user contacts. If your information appears in the device or Outlook address book of a Skype user who chooses to sync their device or Outlook contacts with their Skype contacts, Microsoft may process your data in order to determine whether you are a current Skype user and to allow Skype users to invite you to the service, including via SMS and email.