Update (22Nov2020) Updated API permissions to reflect removal of Exchange app permissions, replaced with Office 365 Exchange Online permissions.

Early June, Microsoft released a new PowerShell module
for managing Exchange Online. This module got announced at Ignite 2019 already, but it took few months between going into preview end of last year before it finally reached Generally Available status. Usage of this module offers substantial improvements over the existing methods to connect to Exchange Online using Powershell, such as:

• Leveraging the PowerShell module ecosystem to install and update the module. This as opposed to the click-to-run Microsoft Exchange Online Powershell Module or connecting through PowerShell remoting.
• Support for Multi-Factor Authentication. This is something which the click-to-run module also offers but is not available when using PowerShell remoting.
• Robustness. Existing sessions could easily timeout when you took a short break from the console. Or worse, your script could terminate in the middle of execution. This required you to reconnect or forced you to add resilience to your scripts by handling with these disconnects from the back end. The cmdlets of the EXOv2 module should be more robust and resilient.
• Introduction of the Graph API support, which should show improvements in terms of speed. Microsoft indicated an 4-8 times improvement should be achievable, but your mileage may vary depending on the operation.
• Support for PowerShell 6/7, core, and non-Windows operating systems is coming.

Exchange Online Management v2 module

The module has been baptized EXOv2 to indicate a major change compared to the click-to-run module (hereafter referred to as EXOv1), and also because it uses Graph API, just like the AzureAD v2 module. The module is available in the PowerShell Gallery, and installation is straightforward. Open a PowerShell 5.1 or later session in elevated mode and run:

Install-Module ExchangeOnlineManagement

The EXOv2 cmdlets which are REST-based and and leverage Graph API have their nouns prefixed with ‘EXO’, e.g. Get-EXOMailbox. Currently, there are 9 EXO cmdlets in the GA module, as well as few additional ones (more on those later). The regular commands such get Get-Mailbox are available as well after connecting to Exchange Online. This is similar behavior to the EXOV1 module, e.g.

Connect-ExchangeOnline [-UserPrincipalName <UPN>]

When required, satisfy the Multi-Factor Authentication logon process, and you
are done. Be advised that the EXOv2 module also supports Delegated Access
Permissions (DAP), allowing partners to connect to customer tenants by
specifying -DelegatedOrganization <mycustomer.onmicrosoft.com> when connecting.

Also note that apart from the EXO cmdlets, the current module also offers few other interesting commands and helper functions apart from the ones for housekeeping:

• Connect-IPPSSession to connect to Security & Compliance center or Exchange Online Protection, depending on licensing. This command was also available in EXOv1.
• Get-UserBriefingConfig & Set-UserBriefingConfig. These are a bit out of context, as these commands allow you to enable or disable the Cortana Briefing for users.
• IsCloudShellEnvironment indicates if you are running from PowerShell or Azure Cloud Shell, which might be useful in scripts to determine the current context.

The EXOv2 cmdlets and their regular equivalents are shown in the table below:

EXO v1 or Remote PowerShell	EXO v2
Get-Mailbox	Get-EXOMailbox
Get-MailboxFolderPermission	Get-EXOMailboxFolderPermission
Get-CASMailbox	Get-EXOCASMailbox
Get-MailboxFolderStatistics	Get-EXOMailboxFolderStatistics
Get-MailboxPermission	Get-EXOMailboxPermission
Get-MobileDeviceStatistics	Get-EXOMobileDeviceStatistics
Get-Recipient	Get-EXORecipient
Get-RecipientPermission	Get-EXORecipientPermission

What you might notice is the absence of any Set-EXO* cmdlets. This is true, and there is no word yet on if and when Set cmdlets will be introduced. That said, the biggest speed gain is often in bulk retrieval of data, not so much in altering one or more attributes. Until then, do not
despair though, as you can pipe output of the EXO cmdlets to their regular cmdlet,
e.g.

Get-EXOMailbox michel | Set-Mailbox -EmailAddresses @{Add='michel@myexchangelabs.com'}

This construction will also provide the additional benefit of parallel processing of objects as they pass through the pipeline, but more on that later.

Now comes another thing you should be aware of, and that is that these EXOv2 cmdlets might not use the same parameter sets as their v1 equivalent. Simply said, you cannot perform a simple Find and Replace operation in your script replacing Get-Mailbox with Get-EXOMailbox to start enjoying benefits of the new module.

When running a cmdlet like Get-EXOmailbox, you might notice that it returns only a subset of the attributes you might expect. Similar to what Properties does for Active Directory module, the EXOv2 module requires you to specify the individual Properties to return. Alternatively, you can use PropertySets to select a predefined set of attributes. For example, Get-EXOMailbox supports PropertySets such as All, Minimum (default), Policy, Quota and Retention to name a few. When needed, you can combine PropertySets, so something like the following is possible:

Get-EXOMailbox -Identity michel -PropertySets Quota,Policy

A small note on the PropertySet All: Just like Get-ADUser .. -Properties
* is considered bad practice as you can impact resource usage and usually return more than what you need, using -PropertySets All for every call is also a bad idea. All is convenient, but make sure you only return the data you need. Be a good person.

To see which EXOv2 cmdlets support PropertySets, use:

(Get-Command -Noun EXO* -Module ExchangeOnlineManagement).Where{$_.Parameters.propertySets}

Performance

Now, I suppose we want to get an indication of the performance enhancements by comparing EXOv2 and equivalent operation using v1 cmdlets. In this simple example we are returning quota information for some 50.000 mailboxes:

In this case, it is not the 4-8x improvement, but more than twice as fast is significant nonetheless. Especially if you are running interactively. To see the impact of parallel processing in the pipeline, we run the following:

As shown, there is a substantial increase in performance, but of course your mileage may vary depending on things like the number of objects, the attributes you require, and any filtering
applied. Note that the PropertySet StatisticsSeed used in the example is a very minimal set of attributes which you can use if you only wish the refer to the objects, such as userPrincipalName, primarySmtpAddress and externalDirectoryObjectID.

Speaking of filtering, one would expect that server-side filtering (-Filter) would show an improvement in terms of speed over client-side filtering (Where), as filtering at the source is far more efficient in terms of result set and data to send over. However, it seems that due to the nature of a shared environment, sending superfluous data over the wire is less of a penalty than local filtering. Of course, your mileage may also vary here, so experiment what works best for your situation. Also, not every attribute is supported for filtering with these EXO cmdlets, which lies in how Graph exposes data. More information on that here.

When your session times out or disconnects, you will see that the module tries to reconnect your session; something which you would have to programmatically solve for the v1 module or regular remote PowerShell:

Certificate-based Authentication

Exchange administrators often have a requirement to run unattended scripts against Exchange Online, for example scheduled reports or as part of another process. In the past, this lead to setups where service accounts and stored credentials were used. Later this was improved by the ability to apply Conditional Access to limit these logons to on-premises infrastructure.

The problem with Multi-Factor Authentication is that it requires interaction with end-user to approve the sign-on. Of course, while your token is still valid, you can easily (re)connect to Exchange Online just by providing the Username Principal Name, which will reuse the token if it didn’t expire. But all in all, these solutions are high maintenance, and far from ideal from a security perspective.

Here comes certificate-based authentication, which is supported in version 2.0.3 and up of the EXOv2 module. In short, certificate-based authentication allows you to log on to Exchange Online using:

• PowerShell
• EXOv2 module
• A (self-signed) certificate containing private key
• Enterprise App registration in Azure Active Directory which contains the public key of this certificate, and proper assigned Azure AD role(s).

Note: Enterprise app registration may require Azure AD P1/P2 license.

To install the EXOv2 2.0.3 version of the module (preview at time of writing), use:

Install-Module ExchangeOnlineManagement -AllowPrerelease

Note that it might complain if you have the GA version of the module installed, in which case you need to uninstall the GA module first, or you can install them side-by-side by specifying -Force.

Next, we need to create a self-signed certificate. To accomplish this, we can use the script published here. To create the certificate, simply use:

.\Create-SelfSignedCertificate.ps1 -CommonName 'EXOv2' -StartDate 7/30/2020 -EndDate 7/30/2021

Note that you need to provide a password to protect the PFX file containing the private key. Also do not forget to import the PFX in your local certificate store. When importing, you can mark the certificate as non-exportable, which prevents admins to transfer the certificate to other systems.

Import-PfxCertificate -CertStoreLocation Cert:\CurrentUser\My -FilePath .\EXOv2.pfx -Password (Read-Host -AsSecureString)

After importing, you can check for the certificate’s presence using:

Get-ChildItem Cert:\CurrentUser\My | Where {$_.Subject -eq 'CN=EXOv2'}

The Subject should be the CommonName you used when generating the certificate. The thumbprint of our certificate is 49A4A73B4696718676770834BCD534DE35030D2C. We are going to use this later on to connect.

Now we need to set things up in Azure Active Directory:

1. Open up the Azure Active Directory Portal, and navigate to Active Directory.
2. Select App registrations, and click New registration.
3. Give the App a meaningful Name, and select Accounts in this organizational directory only. Set Redirect URI to Web and leave the URL blank. Then, click Register.
   
   
   
   Note that our App has been assigned an Application (Client) ID. Make note of this value, as we will need it to connect later on.
   
4. Next, we need to configure the App permissions. Select API permissions. User.Read should show up as default. Click Add a permission, and locate Office 365 Exchange Online from the APIs my organization uses tab. Select Application permissions, and in the next screen expand Exchange and check Exchange.ManageAsApp. We are done here, so click Add permissions.
   
5. Only thing left now is to Grant admin consent, which can be done by clicking Grant admin consent for <tenant>. When done, the Status column for Exchange.ManageAsApp permission should have changed to Granted for <tenant>.
   
   
   
6. Now we need to associate this App with out certificate. Select Certificates & Secrets, and click Upload certificate. Pick the certificate file which we generated earlier, and select Add.
   
   
   
7. Last step is to assign the App one of the built-in Azure AD roles. Go to the Azure Active Directory blade, and select Roles and administrators. Unfortunately, only the following built-in Azure AD roles are supported at this moment:
   
   Global Reader, Global Administrator
   Security Reader, Security Administrator
   Helpdesk Administrator, Compliance Administrator
   Exchange Administrator
   
   Select one of the roles, and click Add assignments in the assignments overview screen. Note that when picking security principals, the App might not show up initially, and typing its first few letters might help. Click Add to assign the role.
   
   
   Note that the UserName mentioned in the overview is the Application ID.

Now we are done configuring the back end, we can look again at connecting. This should now be as simple as running:

Connect-ExchangeOnline -CertificateThumbprint '49A4A73B4696718676770834BCD534DE35030D2C' -AppId '0d3f8f4c-34fb-4a22-8466-80fd7379593b' -Organization '<tenant>.onmicrosoft.com'

Where:

• CertificateThumbprint is the thumbprint of the self-signed certificate you created earlier.
• AppID is the Application (Client) ID of the registered App.
• <tenant>.onmicrosoft.com the initial domain name of your tenant.

Note that you can also connect specifying the CertificateFile instead of Thumbprint, but then you need to provide the password as well via CertificatePassword. Having the certificate in the certificate store of the administrator account or account running the task and just specifying the thumbprint is more convenient and requires zero interaction.

If all steps above were followed correctly, you should now be connected to Exchange Online, without any MFA interaction.

A final note is that Connect-IPPSSession mentioned earlier does not support certificate-base authentication.

What about other Workloads

You can use the same certificate-based authentication to connect to several other workloads as well. That is, provided you have installed the required PowerShell module and the Azure AD role you assigned to the Application has adequate permissions. You can use the commands below to connect to these workloads. A small note that the commands to connect may use a different parameter names for AppId or Organization, e.g. AppId, ApplicationId or ClientId and Organization and TenantId are same things in the examples below.

AzureAD (2.x or Preview)

Connect-AzureAD -CertificateThumbprint '49A4A73B4696718676770834BCD534DE35030D2C' -ApplicationId '0d3f8f4c-34fb-4a22-8466-80fd7379593b' -TenantId '<tenant>.onmicrosoft.com'

MicrosoftTeams (GA or Test)

Connect-Microsoftteams -CertificateThumbprint '49A4A73B4696718676770834BCD534DE35030D2C' -ApplicationId '0d3f8f4c-34fb-4a22-8466-80fd7379593b' -TenantId '<tenant>.onmicrosoft.com'

Microsoft Graph

Connect-Graph -CertificateThumbprint '49A4A73B4696718676770834BCD534DE35030D2C' -ClientId '0d3f8f4c-34fb-4a22-8466-80fd7379593b' -TenantId 'eightwone.onmicrosoft.com'

Audit

The logons which are performed in the context of the Application are viewable in the Azure Sign-Ins at https://aka.ms/iam/rtsp

Note that this view is currently in preview, and there might be a slight delay before logon shows up.

Final Notes

It would be nice if there would be a way to incorporate Exchange granular Role-Based Access Control model into the permissions model. Granting Apps only the built-in Azure AD roles is somewhat limiting, and it would be nice to restrict accounts in only being able to run the cmdlets and parameters they need to use.

When running Exchange cmdlets, you will find these in the audit log but with the <tenant>\AppID as UserName. Therefore, best thing to do is to use a single App registration for each individual administrator or process, instead of using a single App registration and multiple certificates.

And finally, it would be nice if the various teams would align their cmdlet and parameter naming schemes for consistency.