A Skype for Business user can't send an instant message (IM) or call a Skype consumer user if that user's account isn't associated with a Microsoft ID. When this issue occurs, the client displays a junk value (for example, cid-(-767980734670578609)@outlook.com) instead of the display name, and the presence status shows Pending.
An update to the Skype consumer service that was intended to improve performance caused a federation communication issue between Skype consumer and Skype for Business, which affected the accuracy of usernames in contact lists.
This has been fixed in the Skype service. No action is required for end users to benefit from this fix - contact federation between Skype for Business and Skype users functions as intended.