Teams will send chat messages to mailboxes that don't have Teams

The issue is that users in our tenant are able search for and send Teams chat messages to mailboxes and users that don't have Teams.  This includes shared mailboxes and users with Exchange only license. (O1) Neither of those have the ability to log into Teams.

Example

User A searches for User B in Teams, finds User B, and sends them a message which looks like this:

https//filestore.community.support.microsoft.com/api/images/f1b32461-d18a-47eb-bd98-ea6086b74e93

Aside from appearing to be offline, there is no indicator that this user has no ability to respond using Teams. User B isn't left completely in the dark however. Teams will eventually send an email, but it isn't like the ones all of us who have Teams are used to seeing when we leave an unread message for a time.

this is extremely unhelpful for two reasons: First, it doesn't include any of what User A's original message was, and second, try as User B may they cannot log in to Teams to see the activity. At least it lets them who is trying to contact them so they can respond with an email and try to figure out what the original communication was. 

Has anyone else noticed this behavior occurring in their Tenant? My opinion, Teams should not let this behavior occur. At minimum there should be a message saying something like, delivered, user is not valid,  

Is there anyway to make it so Teams won't even show Exchange only and shared mailbox accounts as an option to chat with? 

Thank you for your time, help and advice.

Hello Paul,

I am glad to help you for your concerns here.

First based on your description, I did a lot of research and tests for Teams chat with non-Teams license user. When I tried to search and chat with an Office 365 shared mailbox. The result just as you mentioned, there would be an email delivered to shared mailbox with the notification that " xxxx is trying to reach you in Teams..."

And I also did a lot of research about Teams search performance, as far as I know the Team search based on Office 365 Global Address Book (GAL), as the Nom-Teams license users and shared mailbox are all listed in the GAL, the Teams users would be able to search them and chat. But the respective recipients don't have teams license, and the Exchange Online server would deliver a notification which I mentioned above.  For your concern about " Is there anyway to make it so Teams won't even show Exchange only and shared mailbox accounts as an option to chat with". Just as we talked before, the Teams search based on GAL, from the Tech level, we could make the Exchange Online only and shared mailbox not be searchable for Office 365 users, and just look like split them into a "Seperate organization". However, if this was done,  considered it will affect your Exchange Online users daily work and the development of your company.  So we do not recommended customers make these changes to their GAL. thanks.

On another hand, we do understand if you could directly block the Exchange Online only and Shared mailbox from searching in Teams, it will be more conveient and suitable for your daily work and management. So it is recommended that please give a feedback to Teams UserVoice and leave your good ideas there. This would make the dedicated develop engineers in Microsoft notice this good idea and requirements. And they would consider to directly add this featuer into Teams based on customers feedback in the future, and make our furture daily work and life better, thanks.

Your understanding and patience will be highly appreciated.

Best Regards,

Oliver

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Oliver,

Thank you for the response and confirmation that this is happening in other tenants.  We also thought that the searchability had something to do with GAL and as a result set the Exchange only mailbox and Shared Mailbox as hidden.

https://docs.microsoft.com/en-us/exchange/address-books/address-lists/manage-address-lists

Unfortunately, even though this did successfully hide the addresses/mailboxes from GAL and Outlook, Teams was still able to find them, and it did not resolve the issue.

As you mentioned, this appears to be an oversight on the developers part and is out of our control other than making sure they know via Uservoice.

Here is a link to the bug report in Uservoice https://microsoftteams.uservoice.com/forums/908686-bug-reports/suggestions/39967573-teams-will-send-chat-messages-to-mailboxes-that-do

If you’re experiencing issues do to this, please add your vote.  Thank you.

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Hello Paul,

Thanks for your updates with patience.

For the hidden mailboxes from GAL are still can be searched within Teams, I did a lot of research about this scenario, there are two possible cause for this scenario.

One is after you hiding the mailboxes from GAL, the GAL may not refreshed across your whole organization, so the Teams side may still recognized they are searchable.  And another updates I got is Teams server cache could make Teams users to search the objects ( users) from the search "history". And in this case, you would be able to find the user/shared mailbox which you searched before.

Anyway, just as we talked above, we don't recommend to make the Exchange Online only users or shared mailboxes not searchable from GAL, as this will not be convenient for your organizaiton managment. for example, if you hide the shared mailbox from GAL, it will affect the new users to be added into this shared mailbox, as it cannot be found from GAL etc.

And for your concern don't want users to chat/search with Exchange Online only or shared mailbox within Teams, we do understand it for your daily management. Since you have left a feedback in Teams UserVoice, and this would make the Microsoft develop engineers to notice this scenario and may consider to change it from Teams side in the future.

Your udnerstanding will be highly valued.

Best Regards,

Oliver

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Oliver,

We also looked into both of those possible explinations.  We know the address is hidden in GAL because we gave it a day to sync and confirmed that from Outlook and OWS that the address was no visible/searchable. 

Clearing the local cache was also explored, but it turns out Teams caches things in a ton of different places.   Instead of doing a shotgun approach and clearing out someones entire cache, we decided to try and search for the user via the Teams desktop app on a new computer and via the Teams web app.  In Both scenarios we were able to find the hidden user in teams.

At this point we've given up on being able to prevent this via technical controls and instead have transitioned to administrative controls and user education to try and prevent users from sending teams messages to these accounts. 

We hope that at some future point Microsoft will resolve this issue, but until then I believe this is all we can do. 

Thank you for your time, help, and responses!

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Last updated December 4, 2020 Views 760 Applies to: