Organizing and accessing contact information in Outlook.com
Hi Mark,
The use of contact group is to send an email to multiple people without having to add each name every time you want to write them. Therefore, a contact must have an email address as a requirement to be added in the contact group.
Please note that contacts (with or without emails addresses) can be saved in the contacts folder and in people list in Outlook.com, but cannot be added in the contact group without an email address.
If you have further concerns, feel free to post. We're always here to help.