Oddly the business I work for allows external Skype (personal) contacts to be added and communicated with but does not allow external Skype for Business to be communicated with, even though they can be added.
Apparently if I want to communicate with our clients who also use Office 365 & Skype for Business (even though they are visible in the contact list) we have to go through a process of 'federation' with the client.
Makes no sense to me why we can communicate with world+dog, however our clients who also use Office 365 are a no-no.
Biting the hand that feeds IT
