Controlling the Outlook Monarch Client

Outlook Monarch Controls for the New Outlook for Windows

With the disclosure that Microsoft 365 Copilot will only work with the Outlook Monarch client, organizations interested in Copilot deployments might need to reassess their plans for the “new Outlook for Windows,” currently available in preview.

Because Monarch is under active development, the set of features that it supports changes all the time. An assessment of the client software available last September isn’t a good basis for deciding how ready Monarch is today (this support page includes a non-exhaustive list of key Outlook features). Apart from adding features for Microsoft 365 users, work is also ongoing to make sure that Monarch can support email accounts for other mail servers.

In a related development, Message center notification MC590123 (updated 20 June) and a support article laid out Microsoft’s plan to use Monarch as the default email and calendar client for Windows 11. The kicker here is the statement that “After this change is implemented at the end of 2024, Users with a Microsoft 365 or Office 365 subscription with access to the Microsoft 365 desktop apps can use the new Outlook for Windows.” With their normal enthusiasm for new software, Microsoft will take every opportunity to make Monarch available to end users. Some would say that they will stuff Monarch down peoples’ throats, but that’s going a tad far for me.

Controls to Block or Allow Access to Outlook Monarch

With Microsoft accelerating its plans for Monarch, administrator thoughts invariably turn to the set of controls available to enable or disable the new client. Microsoft documentation covers this topic (and there’s some interesting information in the FAQ), but here are the essentials together with some PowerShell that you might find useful.

Monarch is based on OWA, so it should come as no surprise that it functions like OWA. For example, a setting is available to disable the client at the access level (what used to be the Client Access Server in on-premises servers). This command blocks access to Monarch for the Terry Hegarty mailbox (account):

Set-CASMailbox -Identity Terry.Hegarty -OneWinNativeOutlookEnabled $False

To disable or enable a set of mailboxes, use either the Get-ExoMailbox (to search against mailbox attributes) or Get-User (to search against Azure AD account attributes) cmdlets and pipe the results to Set-CASMailbox:

Get-User -Filter {Department -eq "IT"} -RecipientTypeDetails UserMailbox -ResultSize Unlimited | Set-CasMailbox -OneWinNativeOutlookEnabled $False

To report the set of mailboxes enabled for Monarch, we can do something like this (unfortunately, Get-CASMailbox doesn’t support server-side filtering against OneWinNativeOutlookEnabled):

Get-CasMailbox -RecipientTypeDetails UserMailbox -ResultSize Unlimited | Where-Object {$_.OneWinNativeOutlookEnabled -eq $True} | Format-Table DisplayName, OneWinNativeOutlookEnabled

An OWA mailbox policy setting is available to block users from adding third-party email accounts (like Gmail) to Monarch. This command updates an OWA mailbox policy to disable personal accounts. The policy is effective with Monarch builds post 30 June.

Set-OwaMailboxPolicy -Identity OWAMailboxPolicy-Default -PersonalAccountsEnabled $False 

And to report the set of mailboxes to which the OWA mailbox policy applies, run:

Get-CASMailbox -RecipientTypeDetails UserMailbox -ResultSize Unlimited | Where-Object {$_.OWAMailboxPolicy -eq "OwaMailboxPolicy-Default"}

Turning Off the “Try the New Outlook” Toggle

Recent Outlook for Windows builds include a toggle to allow users to switch to Monarch (Figure 1). If you’re not going to allow people use Monarch, it’s a good idea to remove the tempting toggle.

To hide the toggle, add a new DWORD value in the system registry called HideNewOutlookToggle at HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\General and set it to 1 (Figure 2). The next time Outlook restarts, the toggle is gone.

The change can also be made in a GPO using ADMX build 16.0.5401.1000 or later. The setting is “Hide the “Try the new Outlook” toggle in Outlook,” which sets HideNewOutlookToggle at HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook\Options\General to either 0 or 1, depending on if the toggle is on or off. Publishing the change via a GPO might take a little time before the client responds and disables the toggle.

Reporting Outlook Client Usage

Currently the Email Apps report in the usage reports section of the Microsoft 365 admin center doesn’t separate Monarch out from OWA when it identifies the different Microsoft clients that connect to Exchange Online (Figure 3). Hopefully, Microsoft can update the report to highlight people who use Monarch.

Monarch’s Coming. Are You Ready?

It seems like Microsoft has been on the journey to deliver the new Outlook for Windows forever. But let’s face it, replacing a client that’s been in use since 1997 is difficult to say the least. Code developed over decades can’t be replaced without huge engineering effort, especially when the desired outcome is a common Outlook code base that will work on multiple platforms and support faster innovation.

OWA introduces new functionality much faster than the legacy Outlook for Windows does. That’s not the fault of the older Outlook client. It is handicapped by decades of building features one step at a time. The new Outlook for Windows will eventually be a good replacement. The question is just when that time will be. In the meantime, some Outlook Monarch controls are a good thing to have.