1) Open Outlook.

2) In the top left-hand corner, click New and choose Contact.

3) Fill out all of the needed information, as follows. Then, click Save & Close.

• Name: Add any name (for example, Spam 1)
• Email: Add a fake email address. If you do not add an email address, this process will not work.
• Phone numbers: Add the phone numbers that you want to block. If you need to block more than four numbers, you can use the drop-down arrows to pick other options.

4) Open Skype for Business.

5) Search for the contact that you just created.

6) Right-click on the contact's name and choose Change Privacy Relationship. Then, click Blocked Contacts.

Outcome

All phone numbers associated with the created contact will no longer be able to call or IM you through Skype for Business.