How to add a shared mailbox as additional account in Outlook 2016 (build 8431 and above) on Windows 10 (1709 and above)

The question of adding your shared mailbox(es) in Outlook remains one of the most common ones, mainly because Microsoft has failed to put a proper guidance on the differences between adding a shared mailbox as additional mailbox vs adding it as additional account. To address this, I posted the How to add a shared mailbox as additional account in Outlook article few years back.

The method outlined in the above article still works, but as software moves forward, there have been some changes in the UI that might confuse people, so I decided to put an updated article. I’m not very good at keeping notes on what changed when, so the Office version number I posted in the title above reflects the currently installed on my machine (version 1708 build 8431.2215). This is NOT the first version to have the new “add account” experience. The steps however should work for every version that features the new look and feel for the add account dialog.

Apart from the changes in Outlook, some additional changes in the process can be seen due to the deeper integration with Windows 10 Fall Creators Update (version 1709 or later). In a nutshell, instead of using it’s own ADAL controls, Office 2016 running on Windows 10 will now “offload” the process of obtaining a token to the built-in Windows controls. Generally speaking, the process works, but as static dialogs are used instead of an HTTP render control, the experience will look much different and can cause some confusion. So much for Modern authentication bringing a unified experience across all apps and devices…

Anyway, without further ado, here are the steps to add a Shared mailbox as additional account in newer Office and Windows clients. Start by clicking the File menu, then press the Add Account button:

Outlook add additional account

Alternatively, you can also get to the same dialog by pressing File -> Account Settings -> Account Settings -> New. Either way, you will be presented with the new “add account dialog”:

Outlook dialog

Enter the email address of the shared mailbox there, press the Connect button and wait for the autodiscover process to complete. This might take a while:

Outlook dialog

Once Outlook manages to contact the server, you will be presented with a credentials prompt. Here’s the biggest difference compared to older versions, as at this point Windows will take over and instead of seeing the familiar ADAL credentials prompt dialog, you will be presented with the following:

WAM dialog

This is the most important step of the process. The dialog presented above will ask you for credentials for the shared mailbox, however instead you should provide your *own* credentials, as a delegate. To make this possible, click on the “Sign in with another account” link. You will be presented with the following dialog:

Credentials dialog

Here, make sure to replace the shared mailbox address with *your* UserPrincipalName attribute (as in, the username you use to access Office 365, which might be different from your email address). Once that part is complete, press the Next button.

On the next dialog screen, you will be asked to complete the authentication process. Depending on the settings configured for your organization and the user account in questions, the process might run automatically or require you to provide additional authentication factors. For the sake of simplicity, the below screenshot illustrates the scenario where only a password is used, and the process will be complete once the Sign In button is pressed.

Credentials dialog 2

If everything goes OK with the authentication process, Outlook will be able to fetch the configuration file for the shared mailbox and you will be presented with the following screen:

Account added

And that’s it. The Shared mailbox should now be added as additional account in Outlook and be visible in the left navigation pane. If you get prompted for credentials after Outlook is restarted, make sure to again follow the same process and provide *your* username and password.

Just in case you made it this far without knowing the basics – the process outlined above requires you to have Full Access permissions on the Shared mailbox.

15 thoughts on “How to add a shared mailbox as additional account in Outlook 2016 (build 8431 and above) on Windows 10 (1709 and above)

  1. Tina Li says:

    Thank you! I was trying to help a colleague modify her email signatures by account and wasn’t sure why the alternate account wasn’t showing up in the Signatures preferences. This solved the problem!

  2. Mio says:

    Hey Vasil,

    An issue I’m encountering is that I have a shared inbox with automatic setup. When I try to add the inbox, instead of letting me use my own credentials it just logs me directly into the inbox, which is not as functional for my organization. Do you know of a workaround?

    1. Vasil Michev says:

      You need to remove any auto-mapping, the two methods are not compatible.

      1. Nick says:

        Do you mean for this guide to work (using a office365 account) we need to remove automapping via powersheel first?

        1. Vasil Michev says:

          Yes, as otherwise you will likely run into issues.

        2. Nick says:

          Ok thanks. You should mentioned that in the article. Automapping seems to be on by default for O365 accounts, I assume most people would have automapping enabled by default?
          I’ll look into disabling this, but never used powershell so will have to spend some time setting that up first.

  3. Sach says:

    Good article, the commands to do via PowerShell below.

    $UserCredential = Get-Credential
    $Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri -Credential $UserCredential -Authentication Basic -AllowRedirection
    Import-PSSession $Session

    #Be sure to disconnect the remote PowerShell session when you’re finished. If you close the Windows PowerShell window without disconnecting the session, you could use up all the remote PowerShell sessions available to you, and you’ll need to wait for the sessions to expire. To disconnect the remote PowerShell session, run the following command.
    Remove-PSSession $Session

    #Grant full access to Office 365 mailbox
    $mailboxid1 = “”
    $mailboxid2 = “”
    Add-MailboxPermission -Identity $mailboxid1 -User $mailboxid2 -AccessRights FullAccess -AutoMapping:$false

    #Remove full access to Office 365 mailbox
    Remove-MailboxPermission -Identity $mailboxid1 -User $mailboxid2 -AccessRights FullAccess

  4. Sean says:

    Thanks for sharing this information. I’ve spent quite an amount of time to resolve the issues.
    Now I need to tackle the same issue on Outlook iPhone app.
    Have you ever tried to add the shared mailbox as a new account?
    I got an error message saying “Account already added. Duplicate Account”
    This method seems not working on iPhone app.

    1. Vasil Michev says:

      The above only applies to the Outlook desktop version on Windows. It will not work for mobiles. The Outlook team just announced support (preview) for adding shared mailboxes though.

  5. Fabio says:

    Hello Vasil Michev,
    many thanks for your guide, I’ve followed all this steps but when I press on shared mail box in the left part of outlook I see this message “Impossible to open folders group – …path… – is not a ost file”. How can I solve this problem? Has it ever happened to you? Many thanks & best regards. Fabio.

    1. Vasil Michev says:

      No, I haven’t seen this issue before. I’d double-check whether the user has Full Access permissions, and also make sure no Automapping is configured.

      1. Fabio says:

        Many thanks for your help. Unfortunately automapping is configured. Do you know if it possible add a shared mailbox as account with automapping turned on?

        1. Vasil Michev says:

          Well, the automapped mailbox is interfering, so your best option is to create a new profile and add the shared mailbox directly, using the above method.

  6. Fil says:

    I have set up a shared mailbox as the only account in one of my teammates computers, as she does not need an individual account. It seems to work basically.
    But whenever she tries to search for a mail, the list of results is shown. However, when she tries to open a email, a error message (translated from German):
    “There is a problem opening this element. It may be temporary. If this error occurs again, please restart outlook. A client process has failed.”
    Would you have any idea how to fix this? THanks in advance and best regards!


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