Wednesday, August 3, 2022

Monitoring Azure AD Connect Sync times using Power Automate

For hybrid/federated environments, Azure AD Connect is a crucial service. Azure AD Connect Health provides invaluable information such as alerts, performance monitoring, usage analytics, and other information, but sometimes we need some flexibility on what gets alerted, how, and when.

By default, Azure AD Connect performs a delta sync every 30 minutes. However, what if something happens and it hasn’t been able to perform a sync for 5h? For large organisations, this can be a huge issue as it will impact a variety of services, such as the onboarding of new staff, changes made to groups, changes made to Office 365 services, etc.

In this post, I will show a way of using Graph API to monitor the time Azure AD Connect last performed a sync so we can get an alert when this goes above a specified threshold.

Since we are using Graph API, you will need an Azure App Registration with Organization.Read.All application permissions (check here for other permissions that also work). Once we have our app registration in place, we use the get organization method to retrieve the properties and relationships of the currently authenticated organisation.

If you want to use PowerShell, this is extremely easy with the new SDK. All you have to do is run the following (simplified for brevity reasons):

Import-Module Microsoft.Graph.Identity.DirectoryManagement

Connect-MgGraph

(Get-MgOrganization -OrganizationId "xxxxx-xxxx-xxxxx” -Property OnPremisesLastSyncDateTime).OnPremisesLastSyncDateTime


In this post, however, I’m going to show how to do this, including the alerting, using Power Automate. The first step, after creating a new flow of course, is to schedule it to run at a frequency we desire. In my case, I am running it every 2h because I want to be alerted whenever a sync hasn’t happened in over 2h:

 

Next, we need to be able to query Graph API, and for that, we need an OAuth token. There are multiple ways of doing this in Power Automate, so feel free to use whatever method you prefer if you already have one. For the method I have been using lately, first we need to initialise three variables that will contain our Azure tenant ID, the ID of our Azure app registration, and its secret:


Now we send an HTTP POST request to https://login.microsoftonline.com/$TenantID/oauth2/token in order to retrieve our token. In the request, we need to pass our app registration details. Again, there are multiple ways to achieve the same, below is the method I’ve been using:

 

If all goes well, we should now have a valid OAuth token that we can use to query Graph API. Save your flow, test it, and make sure you don’t get any errors. You should see the following in the run history: a status code of 200, and the token details in the OUTPUTS section.

 

Now that we know our flow works successfully in retrieving an OAuth token, we create a new step where we parse the JSON that gets returned by the previous step. This is because we only need the access_token information (listed at the bottom of the previous screenshot). To do this, we use the Parse JSON action of the Data Operation connector. Under Content, we use the Body from the previous step, and under Schema, you can use the following:

{
    "type": "object",
    "properties": {
        "token_type": {
            "type": "string"
        },
        "expires_in": {
            "type": "string"
        },
        "ext_expires_in": {
            "type": "string"
        },
        "expires_on": {
            "type": "string"
        },
        "not_before": {
            "type": "string"
        },
        "resource": {
            "type": "string"
        },
        "access_token": {
            "type": "string"
        }
    }
}


We can now retrieve the information we want! At the most basic level, we issue a GET request to the following URL: https://graph.microsoft.com/v1.0/organization/our_tenant_id

However, this will return a lot of information we don’t need, so we ask only for the onPremisesLastSyncDateTime by using $select:


Like before, we need to parse the JSON that gets returned so we can more easily use the information retrieved:

 

For the Schema, you can use Graph Explorer to run the same GET request. Then, copy the Response preview and use it as your sample in Generate from sample.



 That will generate the following Schema you can use to parse the JSON:

{
    "type": "object",
    "properties": {
        "@@odata.context": {
            "type": "string"
        },
        "onPremisesLastSyncDateTime": {
            "type": "string"
        }
    }
}

 


We now have all the information we need. I suggest you test your flow once more to make sure everything is working as expected. If it is, you should get the following:


Although INPUTS and OUTPUTS seem identical, by parsing the JSON we now have an onPremisesLastSyncDateTime dynamic property we can use in our flow, something we don’t get without parsing the JSON:


The next step is to check when the last sync happened. Keeping in mind that the returned date/time is in UTC format, we can use the following formula to check if onPremisesLastSyncDateTime is less than (aka older) the current UTC time minus 2h. If it is, then we know the last successful sync happened over 2h ago and we send an alert.

Simply copy-paste the following formula in the first field of you Condition (unfortunately it’s no longer possible to edit conditions in advanced mode):

less(body('Parse_JSON_-_onPremisesLastSyncDateTime')?['onPremisesLastSyncDateTime'],
addminutes(utcnow(), -120))

 

If the result is no, then a sync happened less than 2h ago, so we can successfully terminate the flow. Otherwise, we can send a Teams notification (or email, or whatever method you prefer):



 In this example, I am posting a Teams message to a group chat. For some reason, Power Automate keeps adding unnecessary HTML code even when I write the code myself… Here is the code I am using:


<p>Last Azure AD Connect Sync was <span style="color: rgb(226,80,65)"><strong>@{div(sub(ticks(utcNow()),ticks(body('Parse_JSON_-_onPremisesLastSyncDateTime')?['onPremisesLastSyncDateTime'])),600000000)}</strong></span> minutes / <span style="color: rgb(226,80,65)"><strong>@{ div(sub(ticks(utcNow()),ticks(body('Parse_JSON_-_onPremisesLastSyncDateTime')?['onPremisesLastSyncDateTime'])),36000000000)}</strong></span> hours ago (@{body('Parse_JSON')?['onPremisesLastSyncDateTime']} UTC)!</p>

 

This code produces the following message:


But what are those two weird formulas? That’s how we calculate the difference between two dates and times:

div(sub(ticks(utcNow()),ticks(body('Parse_JSON_-_onPremisesLastSyncDateTime')?['onPremisesLastSyncDateTime'])),600000000)

 

First, we get the current date/time in ticks by using utcNow():

ticks(utcNow())

 

A tick is a 100-nanosecond interval. By converting a date/time to ticks, we get the number of 100-nanosecond intervals since January 1, 0001 00:00:00 (midnight). By doing this, we can easily calculate the difference between two dates/times. Might sound a bit strange, but a lot of programming languages use ticks.

Then, we subtract the number of ticks for our onPremisesLastSyncDateTime property, which tells us how many ticks it has been since the last sync:

sub(ticks(utcNow()),ticks(body('Parse_JSON_-_onPremisesLastSyncDateTime')?['onPremisesLastSyncDateTime']))

 

Lastly, because we don’t want the result in ticks but in minutes or hours, we divide the result by 864000000000 so we get the time difference in minutes, or by 36000000000 to get the result in hours.

 

And there you have it! Now, whenever Azure AD Connect takes over 2h to perform a sync, you will be notified!   😊

Tuesday, February 15, 2022

Create Calendar Event on all user mailboxes

The other day I was asked by our HR department if it was possible to create a calendar event on all user mailboxes. They didn’t want to send a “normal” meeting invite to dozens of thousands of users that people would have to accept, reject, or ignore. All they wanted was a simple all-day calendar event that would notify users about this particular event.

In my opinion, this has always been one of those features I don’t know why Microsoft never added to Exchange. I can think of so many cases where this would be so useful for so many organisations, but here we are. I remembered reading about something like this a few years back, but it turned out I was thinking about the Remove-CalendarEvents cmdlet introduced in Exchange 2019 and Online. This cmdlet allows admins to cancel future meetings in user or resource mailboxes, which is great when someone leaves the organisation for example.

So that was not an option. I thought about using Exchange Web Services (EWS). I’ve written quite a few EWS scripts and that was an option. However, it is all about Graph API nowadays, so that was by far the best option. But can this be done using Graph API? Of course it can! For that, we use the Create Event method:

POST /users/{id | userPrincipalName}/events

POST /users/{id | userPrincipalName}/calendar/events

POST /users/{id | userPrincipalName}/calendars/{id}/events

 

I’ve also written many Graph API scripts and they work great! However, I’ve had to use lengthy functions to get a token, query Graph API, etc., which made these scripts long and complex... However, with the Graph API SDK, this is far from the case! Now it is extremely easy for admins and developers to write PowerShell Graph API scripts! It is really, really straightforward, and no need to rely on HTTP Post requests!

 

Requirements

You will need to have, or create, an app registration in Azure and use a digital certificate for authentication. This link explains how to easily set this up: Use app-only authentication with the Microsoft GraphPowerShell SDK.

The Graph API permissions required for the script to work are 'Calendars.ReadWrite' and 'User.Read.All' (again, if using the -AllUsers switch). Both of type Application.

With the Graph API SDK, you will need the 'Microsoft.Graph.Calendar' and 'Microsoft.Graph.Users' (if using the -AllUsers switch, more on this later) modules. For more information on the SDK and how to start using it with PowerShell, please visit this link.

  

Script Parameters

-UsersFile

TXT file containing the email addresses or UPNs of the mailboxes to create a calendar event on.

 

-ExcludeUsersFile

TXT file containing the email addresses of the mailboxes NOT to create a calendar event on.

Whenever the script successfully creates an event on a user’s mailbox, it saves the user’s SMTP/UPN to a file named 'CreateCalendarEvent_Processed.txt'. This is so the file can be used to re-run the script for any remaining users (in case of a timeout or any other issues) without the risk of duplicating calendar entries.

 

-AllUsers

Creates a calendar event on all Exchange Online mailboxes of enabled users that have an EmployeeID. This can, and should, be adapted to your specific environment or requirement.

The script does not use Exchange Online to retrieve the list of mailboxes. It retrieves all users from Azure AD that have the Mail and EmployeeID attributes populated.

 

Script Outputs

  1. The script prints to the screen any errors, as well as all successful calendar entries created.
  2. It also generates a log file named ‘CreateCalendarEvent_Log_date’ with the same information.
  3. Whenever it successfully creates an event on a user's mailbox, it outputs the user's SMTP/UPN to a file named ‘CreateCalendarEvent_Processed.txt’. This is so the file can be used to re-run the script for any remaining users (in case of a timeout or any other issues) without the risk of duplicating calendar entries.
  4. For any failures when creating a calendar event, the script writes the user's SMTP/UPN to a file named ‘CreateCalendarEvent_Failed.txt’ so admins can easily analyse failures (the same is written to the main log file).

 

Notes

When using the -AllUsers parameter, the script uses the Get-MgUser cmdlet to retrieve Azure Active Directory user objects. I decided not to use Exchange Online cmdlets to keep things simple and because I wanted only mailboxes linked to users that have an EmployeeID. Obviously, every scenario is going to be different, but it should be easy to adapt the script to your specific requirements.

One thing I found, was that running Get-MgUser against a large number of users (in my case, 25000+ users), PowerShell 5.1 was crashing for no apparent reason. Other users on the internet were having the exact same problem when running for a few thousand users. It turns out PowerShell 5.1 default memory allocation will cause the script to crash when fetching large data sets… The good news is that it works great with PowerShell 7+!

The script is slow... When I ran it for 37000+ users, it took approximately 1 second per user. Need to look into JSON batching to create multiple events in one single request.

The script will throw errors in an Hybrid environment with mailboxes on-prem (as they are returned by Get-MgUser). If this is your case, you might want to use an Exchange Online cmdlet instead of Get-MgUser (or get all your mailboxes and then use the -UsersFile parameter).

 

Script

You can get the script on GitHub here.

 

Examples

C:\PS> .\CreateCalendarEvent.ps1 -AllUsers

This command will:

  1. Retrieve all users from Azure AD that have the Mail and EmployeeID attributes populated;
  2. Create a calendar event on their mailboxes. The properties of the calendar event are detailed and configurable within the script.

 

C:\PS> .\CreateCalendarEvent.ps1 -AllUsers -ExcludeUsersFile .\CreateCalendarEvent_Processed.txt

This command will:

  1. Retrieve all users from Azure AD that have the Mail and EmployeeID attributes populated;
  2. Create a calendar event on their mailboxes, unless they are in the 'CreateCalendarEvent_Processed.txt' file.

Friday, October 1, 2021

Unlimited Exchange Online Archiving is no longer Unlimited

TLDR: Microsoft has added size restrictions to Unlimited Archiving (aka Auto-Expanding Archiving). The change will take effect beginning November 1, 2021. Once this limit takes effect, users will not be able to extend their online archives beyond 1.5TB.


Upcoming Changes to Auto-Expanding Archive

MC288051 · Published 29 Sept 2021 · Last updated 30 Sept 2021

 

Message Summary

Updated September 30, 2021: We have updated the content below for additional clarity. Thank you for your patience.

We will be removing the word ‘Unlimited’ from our service description and related public documentation for the auto-expanding archiving feature, and instituting a 1.5TB limit for archive mailboxes. This limit is not configurable.

 

Key points

  • Timing: This change will take effect beginning November 1, 2021 and is applicable to all environments.
  • Roll-out: tenant level
  • Action: review and assess

 

How this will affect your organization

Once this limit takes effect, your users will not be able to extend their online archives beyond 1.5TB. As currently noted in our documentation, auto-expanding archive is only supported for mailboxes used for individual users or shared mailboxes with a growth rate that does not exceed 1 GB per day. Using journaling, transport rules, or auto-forwarding rules to copy messages to Exchange Online Archiving for the purposes of archiving is not permitted. A user's archive mailbox is intended for just that user. Microsoft reserves the right to deny auto-expanding archiving in instances where a user's archive mailbox is used to store archive data for other users or in other cases of inappropriate use.

If you have previously worked with Microsoft Support to provide exceptions for existing archives exceeding 1.5TB, those specific archives will not be affected by this change. You will not, however, be able to create any new archives that exceed 1.5TB.

 

What you need to do to prepare

You should check the size of archives in your organization if you are concerned that they might be close to the limit and consider deleting some of the content if you intend to continue adding to the archive. You can use Get-MailboxFolderStatistics to view archive mailbox size.

Wednesday, July 8, 2020

Exchange Online PowerShell Scripts with Modern Auth

Auditing and reporting scenarios in Exchange Online often involve scripts that run unattended. In most cases, these unattended scripts access Exchange Online PowerShell using Basic Authentication (username and password). However, basic authentication for Exchange Online Remote PowerShell will be retired in the second half of 2021. As an alternative method, Microsoft has recently announced the Public Preview of a Modern Authentication unattended scripting option. As such, if you currently use Exchange Online PowerShell cmdlets in unattended scripts, you should look into adopting this new feature. This new approach uses Azure AD applications, certificates and Modern Authentication to run non-interactive scripts!

 

How does it work?

The EXO V2 module uses the Active Directory Authentication Library to fetch an app-only token using the Application ID, Azure Tenant ID, and a digital certificate thumbprint. The application object provisioned inside Azure AD has a Directory Role assigned to it (like Exchange Administrator), which is returned in the access token. Exchange Online then configures the session RBAC using the directory role information that is available in the token.


Configuring app-only authentication

This feature is still in Public Preview and requires version 2.0.3-Preview or later of the EXO PowerShell v2 module (available via PowerShellGallery).

To install the Preview release of the EXO v2 module, run the following command:

Install-Module -Name ExchangeOnlineManagement -RequiredVersion 2.0.3-Preview -AllowPrerelease

If already installed, you can update an earlier version of the of the EXO v2 module by running the following command:

Update-Module -Name ExchangeOnlineManagement -AllowPrerelease


Step 1: Application registration in Azure AD

  1. Go to the Azure AD portal at https://portal.azure.com/ and sign in with your Azure AD account;
  2. Under Manage Azure Active Directory, click View;
  3. Under Manage, select App registrations and then click New registration;
  4. In the Register an application page that appears, configure the following settings:
    • Name: Enter something descriptive.
    • Supported account types: select Accounts in this organizational directory only (Microsoft).
  5. When you are finished, click Register;
  6. In my case, I called it Exchange Online PowerShell:

 

 

Step 2: Assign API permissions to the application

Next, we need to assign it permissions to manage Exchange Online as an app. An application object has the default permission User.Read. For the application object to access Exchange Online resources, it needs to have the application permission Exchange.ManageAsApp. API permissions are required because they have consent flow enabled, which allows auditing (directory roles do not have consent flow).

  1. Select API permissions;
  2. In the Configured permissions page that appears, click Add permission;
  3. In the flyout that appears, scroll down to Supported legacy APIs and select Exchange:
  1. In the flyout that appears, click Application permissions;
  2. In the Select permissions section, expand Exchange and select Exchange.ManageAsApp and then Add permissions:

  1. Back on the Configured permissions page, click Grant admin consent for “tenant name” and select Yes in the dialog that appears. Ensure the permissions have been granted (green tick):

 

 

Step 3: Generate a self-signed certificate

There are multiple ways to create a self-signed X.509 certificate. You can use the Create-SelfSignedCertificate script or the makecert.exe tool from the Windows SDK for example. Personally, I found the easiest way to be the New-SelfSignedCertificate PowerShell cmdlet. The following example creates a self-signed certificate and places it in my personal certificate store:

New-SelfSignedCertificate -Subject “ExO-PS-Nuno” -KeyExportPolicy “Exportable” -CertStoreLocation cert:\CurrentUser\My -Provider “Microsoft Enhanced RSA and AES Cryptographic Provider”

While we are here, take note of the certificate’s thumbprint as we will need it in the final step.

It might be obvious, but I should mention that the certificate has to be installed on the user certificate store of the computer where you want to connect to Exchange Online from.


Next, export the certificate using the format .CER (we will need it in the next step):

 

 

Step 4: Attach the certificate to the Azure AD application

  1. In the Azure AD portal under Manage Azure Active Directory, click View;
  2. Under Manage, select App registrations;
  3. On the App registrations page that appears, select your application;
  4. Under Manage, select Certificates & secrets;
  5. On the Certificates & secrets page, click Upload certificate:
  1. In the dialog that appears, browse to the self-signed certificate you created in the previous step, and then click Add:

  1. The certificate is then uploaded and added to the application:

 

 

Step 5: Assign a role to the application

One thing to note with this method is the lack of RBAC controls. We simply cannot take advantage of the granular controls Exchange offers with RBAC... Instead, what the service principal can and cannot do is determined by the role it is assigned in the Azure AD portal. We can play with the roles and actions assigned to these role groups, but those changes will obviously affect anyone assigned the same role.

 

Azure AD has more than 50 admin roles available. For app-only authentication in Exchange Online, the following roles are currently supported:

  • Global administrator
  • Compliance administrator
  • Security reader
  • Security administrator
  • Helpdesk administrator
  • Exchange administrator
  • Global Reader

 

  1. In the Azure AD portal under Manage Azure Active Directory, click View;
  2. Under Manage, select Roles and administrators;
  3. Select one of the supported roles. On the Assignments page that appears, click Add assignments;
  4. In the Add assignments flyout, find and select the application, and then click Add:

  1. Our application now has Exchange administrator rights:

 

Step 6: Connect to Exchange Online PowerShell

The final step is to connect using our certificate’s thumbprint. To do this, we run the following cmdlet:

Connect-ExchangeOnline -CertificateThumbPrint “EAB240A72B05FBC980D1259FD21AE099D530F4AF” -AppID “3c2025f6-xxxx-xxxx-xxxx-xxxxxxxxxxxx” -Organization “xxxxxx.onmicrosoft.com”

And there you go!   😊


If you don’t want to install the certificate, you can actually connect using the local .pfx certificate instead:

Connect-ExchangeOnline -CertificateFilePath “C:\Users\nuno\Documents\Exo-PS-Nuno.pfx” -AppID “3c2025f6-xxxx-xxxx-xxxx-xxxxxxxxxxxx” -Organization “xxxxxx.onmicrosoft.com”

 

Important Considerations

As any other action performed in Exchange Online, any changes we do via this new method still results in them being captured in the Admin audit log and, in turn, in the Unified Audit log in Office 365. A downside I should highlight, is that any actions performed using this method will list the application as the user performing the action. As such, it might be a good idea for any admin to have their own application so that actions can be correctly audited and tracked.


Another important thing to keep in mind when using this new method, is that its authenticating flow against Azure AD is not subject to Conditional Access policies and MFA enforcement. While this can be great as it allows us to enable automation, you must take extra care to secure your app details and certificate’s private key, as anyone who gets their hands on them can easily reuse them from anywhere...

Restoring Deleted Items from Exchange as an Admin

The Get/Restore-RecoverableItems PowerShell cmdlets have been available for some time now in Exchange Server 2016/2019 and Exchange Online environments. These allow admins to restore deleted items from user mailboxes such as in the following example:

Restore-RecoverableItems nuno@domain.com -FilterItemType IPM.Note -SubjectContains “New Joiner – John Doe” -FilterStartTime “20/06/2020 12:00:00 AM” -FilterEndTime “21/06/2020 11:59:59 PM”

Items are restored to the original folder location if the information is available for the item. If the information cannot be found, the item is restored to the default folder for the item type (Inbox for messages, Calendar for meetings and appointments, and so on).

What this post is mainly about, however, is the fact that admins can now do the same from the preview version of Exchange Admin Center (with the new UI)!

Important: please note that in order to use these cmdlets and the method described below, you need to be assigned the Mailbox Import / Export permission which, by default, no one is assigned.

To get started, go to the Exchange Admin Center and click on Try it now to access the preview version:

Alternatively, you can use the following link to get to it directly: https://admin.exchange.microsoft.com/#/mailboxes

Next, select the user you want to recover deleted items for and then look for the Recover deleted items link on the user property page:

The new Recover deleted items UI will show up and automatically list the latest 50 recoverable items:

We can easily search for the items we are interested in by subject, type, or folder type:

After clicking Apply filter, our results are reduced to recoverable items containing the subject line “azure” which were deleted within the past 30 days. Once we find the item(s) we want to recover, we simply select it/them and click on Recover deleted items:

Once recovered, a green banner will appear indicating all items have been successfully recovered:

All done!   😊

Friday, June 26, 2020

Exchange LUN disappeared after reboot

After rebooting an Exchange 2013 server to complete the installation of a security update, 2 LUNs just disappeared:


Looking in Disk Management their Status was Failed:


The LUNs were offline, and after manually bringing them online everything was back to normal.

There had been some previous work done on these LUNs in order to expand them and, for some reason, the default Windows policy to make SAN disks offline was applied (it assumes VMware disks are SAN disks).

After changing the policy to make “new” disks online by default, the issue didn’t happen again:

How to set OWA Language and Time zone using PowerShell

When a user first logs on to Outlook Web App (OWA), he/she gets prompted to set their language and time zone:

 

Can we, as administrators, pre-set these for users or change them after they have been set, for example? Of course! To do this, we use the Get/Set-MailboxRegionalConfiguration cmdlet:


The two parameters we are interested for this scenario are:

  • Language: specifies the language setting, such as en-us, that would apply for the mailbox;
  • TimeZone: specifies the time zone, such as Pacific Standard Time, that the mailbox in the specified region uses. The default value is the time zone setting on the server.

Let us say, for example, that we want to set everyone’s mailbox to American English and Pacific time. To do this, all we need to run is:

Get-Mailbox –ResultSize Unlimited –Filter {RecipientTypeDetails –eq "UserMailbox"} | Set-MailboxRegionalConfiguration –Language en-US –TimeZone "Pacific Standard
Time"

How to Change Exchange EAC Language

When we first login to the Exchange Admin Center (EAC), we are greeted with the language selection screen and time zone. But how do we change EAC’s language after that? The answer is to use Outlook Web App (OWA). Once you have logged into OWA, select the cog icon in the top right hand corner and then click Options:


Next, go to settings in the options menu, and on the right hand menu select regional. Now edit the language and time zone settings to what you want as these settings also apply to the EAC:


But what about for environments where administrators do not have mailboxes? How do they change EAC’s language if they do not have access to OWA? In this case, you can specify the language you want to use in the URL itself. For example, for American English, add ?mkt=EN-us to the EAC’s URL: https://mail.domain.com/ecp?mkt=EN-us

This works for both on-premises Exchange 2013 and above, and Office 365.

Thursday, June 25, 2020

How to Disable Microsoft Stream

As an Office 365 Global Admin, you can prevent some or all users in your organisation from being able to use Stream. This is typically done in cases where employees are already using Office 365 Video or if Stream has not been approved by all parts of your organisation.

When a first user from any organisation signs-up for Microsoft Stream using their corporate credentials, Microsoft Stream service is registered as an application in the organisation's Office 365 tenant. The license is automatically assigned to the user who signed up. There are additional licenses available for the IT admin to assign to other users in the organization without them going through the sign up process.

Important: as an admin, you can unlicense users from the Office 365 admin center. However, even though you might have removed Microsoft Stream license from a user, they have the option to sign-up via a free trial and get access to your organisation's Stream portal.

 

To turn off Microsoft Stream for everyone, follow these steps:

  1. As an Office 365 Global Admin, log in to the Azure portal;
  2. In the Azure Active Directory (AAD) section, click Enterprise Application, and then in the Manage section, click All Applications;
  3. Change the filters to Show All Applications with All Application Status, and then click Apply;
  4. Search for Microsoft Stream Service from the list of applications, or search by the GUID 2634dd23-5e5a-431c-81ca-11710d9079f4 for Microsoft Stream Service:
  1. Click the Microsoft Stream Service application, and then under Manage, click Properties;
  2. Set Enabled for users to sign-in flag to No;
  3. Click Save:

 

You have now blocked access to all users for Stream. When a user now tries to access Stream, they will receive the following error message: