Skype / Teams interop and hybrid, explained

The coexistence and interop between Skype for Business (Online and on-prem) and Teams have been an interesting topic since the day Microsoft Teams was introduced. It is not a new topic, but I feel it still needs clearing up. Hopefully this could help people and businesses understand the possibilities and implications, and in turn get the most out of the Microsoft UC stack, and have a smoother ride on their migration journeys.

So, can Skype and Teams live together in harmony? Yes, absolutely, as long as you get the coexistence configuration right.

There are 5 options, available as policies in Teams Admin Centre (TAC), when it comes to coexistence mode:

The fundamental here is peer-to-peer communication. From which platform does it start at the sender’s end, and where does it land at the receiver’s end. This applies to both Skype for Business Online and on-prem.

Let’s take a closer look at the modes and how do they work.


Users can run Skype for Business and Teams clients on their computers side-by-side. The 2 will operate independently to each other. All peer-to-peer communication (IM and call) will start and land in the same platform. No crossing.

Edit: 21/05/2020

This also applies to presence information. Skype for Business and Teams clients operate independently. The presence information in one platform does not try to match or sync with other one. The user can manually set presence, independently, in both Skype for Business client and Teams client. Other users will see presence information in the respective platform.

On top of that, users can generate and send out meeting invites from either platform.

Edit: 12/06/2020

A new policy parameter was added to CsTeamsMeetingPolicy (MC214700, 30 May 2020) to allow users in Islands mode set Outlook to only create Teams meetings.

The new parameter is PreferredMeetingProviderForIslandsMode. The default value is TeamsAndSfB, where both Teams and Skype for Business Outlook meeting add-ins are enabled.

You can set the meeting add-in preference to Teams by setting the parameter to TeamsOnly.

I would suggest you create a new Meeting Policy for good practice.

And use the Grant cmdlet to assign policy to users.

Please note, by setting the preference in the above policy, you’d only disable the Skype for Business Meeting Outlook add-in. The action will not trigger any meeting migration. It does not change existing Skype for Business meetings to Teams meetings. And vice versa, you can set the preference back to TeamsAndSfB and it will not change any Teams Meetings to Skype Meetings.

Is this good? Is this bad? We’ll discuss later on in this article. Let’s get the different modes out of the way.

Skype for Business with Teams Collaboration

Again, users can run Skype for Business and Teams client side-by-side. However, Teams client now only provides the “collaboration” features, which are teams and channels. There is no peer-to-peer IM or call, and no meeting function.

Edit: 21/05/2020

Presence information in Skype for Business take precedence over Teams. User’s Skype for Business presence is synced to their Teams client. Users are not able to manually set presence in Teams. E.g. If the user only have Teams client running, his/her Teams client will show as “Offline” and unable to be manually changed because Skype client is not logged in.

Skype for Business with Teams Collaboration and Meetings

Very similar to the one above, but this time Skype for Business don’t do meetings anymore. Users will generate and send out Teams meeting invites. Peer-to-peer IM, presence and calling remain in Skype for Business.

Edit: 21/05/2020

Presence information in Skype for Business take precedence over Teams. User’s Skype for Business presence is synced to their Teams client. Users are not able to manually set presence in Teams.

Skype for Business only” and “Teams only” are quite self explanatory. Users either use ALL communication modalities in Skype or everything in Teams. Only one of the two client software is needed on the user’s computer.

Edit: 21/05/2020

The presence information from the respective platform is the effective presence for the user.

Edit: 12/06/2020

A few words on meeting migration behaviour. By default, a meeting migration is automatically triggered when a user is set to “Teams Only” or “Skype for Business with Teams Collaboration and Meetings“. This means the Microsoft Meeting Migration Service (MMS) will go through user mailboxes in Exchange Online and automatically update existing Skype for Business meetings to Teams meetings (new invites will be sent out). However, there is one catch: MMS is only triggered when the coexistence policy is applied at user level. So if you set it at org-wide/tenant level, the MMS will not do anything and no Skype for Business meeting will be updated to Teams meeting.

Which one should you use?

First of all, Islands mode is BAD! Although it is the default mode in 365 tenancy, it’s bad. Don’t get me wrong, it is there for a reason. It’s good for a very small group of pilot power users to try out Teams without doing or taking any consideration to Skype, but it’s bad to be put in production or applied to a wide user base. We’ll explain why, read on.

The principle when considering coexistence modes is that whatever you choose, do not have overlapping functionalities between Skype and Teams. For example, peer-to-peer IM, presence, and calling, make it only one of the two can do it, not both. Put yourself in the users position, if you find yourself facing a choice between the two when you try to use a specific feature you’ve got it wrong.

In many scenarios, businesses would have a mixed population of users running different coexistence modes. It could be a phased migration, or people/business want to take advantage of Teams meetings while their main communications platform remains on Skype for Business. (Want to know what’s the advantage? Read this.) This is where the fun starts, and where the benefit of getting coexistence mode right shines through.

To put your organisation in this mixed mode, you need to set one org-wide coexistence mode (not Islands) for the majority and apply user level policies to the subsets of users who need different modes. Setting the org-wide policy is quite straightforward and can be done in the TAC. To set the user level policy, TAC can only operate on one user at a time, so if you want to apply to bulk users you’d need to use PowerShell.

Now, let’s see how would those different coexistence modes interop with each other.

I made the diagrams below with directional arrows to indicate where does the communication start from and where does it land at the end. They are all “vice versa”.

See, as long as the coexistence modes are set correctly everyone can chat and call everyone else. The communication can flow across the two platforms without problems.

What happens when it’s not set right? Let me show you, and you will see why Islands mode is bad.

You see, in Islands mode people can run the two clients side-by-side at the same time. The problem is, they don’t always do. Islands mode can work, as long as everyone always have both Skype and Teams running to avoid un-deliverable peer-to-peer communications. Islands mode can work, but with a great risk of human error. Let’s be honest here, us humans are not as reliable as computers.


If you have a Skype for Business on-prem server deployment, you may wonder when/if you’d need to put hybrid in place to enjoy some Microsoft Teams goodness.

Skype for Business hybrid was originally created to allow users homed in Skype Online to communicate with users homed on the Skype on-prem server of the same organisation, and of course migrating from Skype on-prem to Skype Online.

Similar principle applies when it comes to Teams and Skype for Business on-prem. You will need hybrid if peer-to-peer communication (IM, presence, and calling) across the 2 platforms is required.

For example, when partial user base of an organisation is homed on Skype for Business on-prem server with coexistence mode set to “Skype with Teams Collaboration”, and the rest of that user base is homed on Microsoft Teams with coexistence mode set to “Teams only”.

Another approach is “Meetings First”, where organisations move their meeting workload into Teams while continuing to use Skype for Business on-prem server for peer-to-peer chat, presence, and calling.

In this scenario, all users are homed on the Skype for Business on-prem server; they would have their coexistence mode set to “Skype for Business with Teams Collaboration and Meetings”; they would have Skype for Business client and Teams client running side-by-side on their computers with no overlapping modalities.

As you can see, in this case the workloads are actually independent of each other. The users just have different modalities of their systems connected to different back ends. No user is actually homed in the cloud (AD Deployment Locator points to on-prem) and no peer-to-peer communication is going across Skype for Business and Teams, or across on-prem and Microsoft cloud. Therefore, hybrid is not mandatory in this configuration. The minimum requirement is the on-prem Active Directory to be synced with Online via AAD Connect.

Having said that, it is still a good practice to have hybrid in place at this stage. Why? To pave the road for next phases. Organisations normally use “Meetings First” to ease their way into Teams migration. And to complete a full migration, you guessed it, hybrid configuration is required. And if you choose to go through a phased migration, which most organisations would, you’d need hybrid to cope with the split user base period.

There. It was a bit long winded but I hope made things a bit clearer around Skype/Teams coexistence, interop and hybrid.

I hope I have been helpful. Thank you for reading.


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