In July 2018, we will no longer support the use of Session Border Controllers (SBC) to connect 3rd Party PBX systems to Exchange Online Unified Messaging (UM). We’re making this change to provide a higher quality of service for voicemail, using Exchange standard and Skype for Business protocols. Customers considering a new deployment of this scenario should be aware that they will have a little less than a year to complete one of the migrations below. Customers with existing deployments remain fully supported until July 2018, including moving voicemail-enabled mailboxes from Exchange on-premises and voicemail-enabling new mailboxes.
The following configurations are not affected by this change:
Skype for Business Server (on-premises) connected to Exchange Online UM
3rd party voicemail solutions that deposit voicemail messages into Exchange Online mailboxes through APIs, rather than an SBC connection
All forms of Exchange Server UM (on-premises)