BLOG 12 March 2021

Avoid the Microsoft Teams “Islands Mode” Trap Part 2

After some issues related to Guest Access Features in Microsoft Teams related to the Upgrade Mode configuration, I decided to update this article.

Update guidance to control Guest Features.

After some issues related to Guest Access Features in Microsoft Teams related to the Upgrade Mode configuration, I decided to update this article.


The actual problem with Teams Guest Access Features is related to the fact that the Upgrade Mode at Organizational Level not only dictates what Upgrade Mode is configured by default for users, but this setting also dictates what features Teams Guests have in your tenant.


So effectively this single Organizational Settings configures two settings or features at once: The Upgrade Mode for Users and the Feature Set for Guests. 


This is a horrible thing and hard to understand why there is just one switch for both features, in an ideal world there would be two settings, unfortunately this is not the case and we are stuck with just this one setting to represent both.



This means if you want Guests to have access to Chat and Calling features the Upgrade Mode cannot be configured with a Skype for Business Upgrade Mode.  This is a huge disappointment for managed upgrades to Microsoft Teams when Guests need the missing features.


In case Guests need Chat and Calling it may be better to configure the Upgrade Mode to Teams Only or Islands Mode and configure all users needing Skype for Business Upgrade Modes individually.  Not ideal as one should not forget to configure users correctly whenever a user is added to Skype for Business or Teams.


The downside of cycling through a long list of users and assigning Policies one at a time with PowerShell is cumbersome and takes a long time (eventually times out and you must restart the PowerShell script)


Luckily, Microsoft made it possible to configure users in batch instead of performing policy changes one after the other.  You can assign a Policy to a batch of users or to a group of users, this dramatically decreases the amount of time it takes to assign Policies to a large group of users and more importantly this will not time-out.

This is an example of assigning a Policy to a list of Users:


$users_ids = @("","","") New-CsBatchPolicyAssignmentOperation -PolicyType TeamsUpgradePolicy -PolicyName SfBWithTeamsCollab -Identity $users_ids -OperationName "Batch Assign Upgrade Modes"

This is an example of assigning a Policy to a Group of users:

New-CsGroupPolicyAssignment -GroupId d8ebfa45-0f28-4d2d-9bcc-b158a49e2d17 -PolicyType TeamsUpgradePolicy -PolicyName SfBWithTeamsCollab -Rank 1

Dead Ends with Islands Mode 

While Islands Mode is already confusing enough for users that are using Microsoft Teams it even worse for users not using Microsoft Teams.  This may sound unexpected but Islands mode configuration for users not having a Teams License and not using Microsoft Teams is a dead-end configuration and users are left in the dark.


The problem originates from the fact that Islands Mode is not aware of Skype for Business Modes at all, this is the mode where Teams talks to Teams. Now many customers are still in pilot for Microsoft Teams and are controlling what users are using Teams and what users are not, most of the customers are not controlling the Upgrade Modes they are just going along with the default.


This is a recipe for disaster as there is usually one Upgrade Mode configured for the entire Organization as Islands Mode, some users are in a pilot to trial Microsoft Teams, and all other users are still using Skype for Business, but they are configured as Upgrade Mode with Islands Mode (as dictate by the Organizational Wide Policy) The important fact is usually that they do not have a valid Microsoft Teams License.  At this point things are going sideways, and users are going to be confused.


I am just highlighting two of the major issues you will see in this configuration.


A Teams Islands user sending a message to a Skype for Business Islands Mode user (not using Teams or having a valid license) First of all the Teams Islands user does not know or does not see the receiving user does not have a valid Teams License and Microsoft Teams does not show an issue when sending a message.



The Skype for Business users receives a missed chat in the Inbox because he is not using Microsoft Teams.



When he is clicking on “Go to conversation” he does not end up anywhere as he does not have a License to start using Microsoft Teams



A Teams Islands Mode user calling a Skype for Business Islands Mode user (not using Teams or having a valid license) The call will end up in Voicemail.


This table highlights all the different combinations including taking Teams Licenses into account.



The conclusion is that using Islands Mode as the Upgrade Mode for your organization will cause a lot of issues.  It is a tricky slope when Islands Mode is your preferred mode. If your organization still decides to use Islands Mode, then the golden rule is to configure every user the same and have everyone start using Microsoft Teams at the same time, not just your pilot users.  If your organization is not ready to do this, then Islands Mode is not your path forward and you should revert to the proper Upgrade Modes and enjoy the predictable communications at all times.

More information can be found through the following links.

Missed the first part of our blog? You can read it here:

Johan Delimon



  • Teams Voice
  • Teams Meeting Rooms



  • Microsoft Teams & Skype for Business MVP, MCSM, Microsoft Trainer, Enterprise Architect & Community Leader
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