You can turn on alerts for incoming instant messages (IMs), voice mail messages, and missed IMs or missed calls for Lync ...

You can turn on alerts for incoming instant messages (IMs), voice mail messages, and missed IMs or missed calls for Lync Mobile users using a push notification service instead of Microsoft Office 365 to send those alerts. Depending on your supported mobile devices, you can use the Microsoft Push Notification Service, the Apple Push Notification Service, or both.