Which coexistence mode allows users to evaluate Microsoft Teams while maintaining PSTN calling using the Skype for Business client?

The coexistence mode referred to in this scenario is the Islands mode. In this mode, users in the organization can use both Microsoft Teams and Skype for Business simultaneously. This setup allows individuals to evaluate Microsoft Teams while still retaining the ability to make and receive PSTN (Public Switched Telephone Network) calls through the Skype for Business client.

In Islands mode, users can initiate chats and meetings in either platform, depending on their preference, while keeping the existing Skype for Business functionality intact for calling. This dual capability is particularly useful during a transitional period when organizations are moving from Skype for Business to Microsoft Teams, allowing for a gradual adoption of Teams without losing essential features immediately.

Other coexistence modes may impose different limitations or requirements that do not support the same flexibility regarding PSTN calling. For example, some may focus more on either Teams or Skype for Business, which would not provide the necessary evaluation opportunity for Teams while maintaining PSTN capabilities.