Controlling Who Receives Invitations to Teams Channel Meetings

Teams Channel Meetings Available to all Members

I wrote about who receives invitations for Teams meetings in March 2020. Looking back, that was at the start of the Covid-19 pandemic and the massive upsurge in online meetings and usage that propelled Teams to its current level of 300-plus million monthly active users. In any case, people were very interested in figuring out who receives invitations to meetings, and the article is very popular.

A recent question noted that “despite scheduling a Channel meeting, all people that belong to the channel still get an invitation email and the block on the calendar to the meeting created.” The question is why did team members receive invitations?

Apart from discussing the mechanics of creating meetings, Microsoft’s documentation isn’t much help about invitations sent for Teams channel meetings, so let’s probe further. As you’ll recall, Teams supports private meetings created by users with a defined participant list and channel meetings that are open to anyone in the team to attend. When you create a meeting and add a channel, you can specify if team members should receive invitations that add the meeting to their calendar (Figure 1).

If you select the option to invite members, Teams generates meeting invitations and sends them to all team members. Going back to the original question, it could be that this is what happened and the user simply forgot that they had asked Teams to notify the other team members.

The Group Subscriber List and Teams Channel Meetings

But life isn’t simple and the obvious answer probably doesn’t apply. Every team has an underlying Microsoft 365 group. Each group has a subscriber list composed of members who want to receive details of messages and events sent to the group. This functionality is directed at Outlook groups, which communicate via email, rather than team-enabled groups, which use channel conversations instead.

By default, the group’s AutoSubscribeNewMembers setting is set to False for team-enabled groups. This tells Exchange Online to not add new users to the group’s subscriber list when they join. However, it’s possible that groups which started out as Outlook groups before they became team-enabled have AutoSubscribeNewMembers set to True, meaning that new users join the subscriber list and receive updates for events like invitations to new Teams channel meetings.

Checking Teams that Auto-Subscribe New Members

To discover if auto-subscription of new members happens for the teams in your tenant, run this PowerShell code:

Connect-ExchangeOnline
[array]$Groups = Get-UnifiedGroup -ResultSize Unlimited -Filter {ResourceProvisioningOptions -eq "Team"}
If ($Groups) {
   [int]$i = 0; [array]$GroupNames = $Null
   ForEach ($Group in $Groups) {
     If ($Group.AutoSubscribeNewMembers -eq $True) {
        Write-Host ("Team {0} autosubscribes new users" -f $Group.displayName)
        $i++
        $GroupNames += $Group.displayName
     }
   }
   Write-Host ("{0} teams of {1} autosubscribe new users found ({2})." -f $i, $Groups.count, ($GroupNames -join ", "))
}

Much to my interest, I discovered that 57 teams in my tenant auto-subscribe new members. Many of the underlying groups date back to the earliest days of Office 365 groups and were subsequently team-enabled since.

I suspect that auto-subscription is the root cause for the reported problem. If this is true, the easy fix is to reset the AutoSubscribeNewMembers setting for the affected teams and remove users from the existing subscriber list. This code does the job and makes sure that channel meeting invitations only go to team members if explicitly chosen by the meeting organizer:

$Teams = $Groups | Where-Object {$_.AutoSubscribeNewMembers -eq $True}
ForEach ($Group in $Teams) {
  Write-Host ("Resetting autosubscription setting for {0}" -f $Group.displayName)
  Set-UnifiedGroup -Identity $Group.ExternalDirectoryObjectId -AutoSubscribeNewMembers:$False
  [array]$Links = Get-UnifiedGroupLinks -Identity $Group.ExternalDirectoryObjectId -LinkType Subscribers
  Remove-UnifiedGroupLinks -Identity $Group.ExternalDirectoryObjectId -LinkType Subscribers -Links $Links -Confirm:$False
}

Another Approach for Teams Channel Meetings

If you don’t want to remove subscribers from groups, another solution exists. You can create a private meeting in Teams or Outlook (with at least one participant). After Teams creates the online details for the meeting, copy and paste the link to the call along with other details of the meeting into a channel conversation (Figure 2). At the appointed time, any members who want to join the call can click the link to connect.

The advantage of this approach is that it works for any kind of channel – regular, shared, and private (the meetings won’t show up in the calendar app). The technique relies on the fact that you’re posting details of a private meeting into a conversation. People who want to attend have the option of copying the details into their calendar so that they’ll be reminded of the call.

All of this proves that Teams is built on a foundation of other services and that sometimes those services are the reason why something unexpected happens in Teams. It also proves that there’s often another way to accomplish a task. Which is kind of nice.

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