Shared Mailbox Member Management: Bulk Assign from User Profile & Intermittent First-Time Save Failure

Question

Shared Mailbox Member Management: Bulk Assign from User Profile & Intermittent First-Time Save Failure

Erick 0

I would like to report a bug and suggest a workflow improvement regarding Shared Mailbox members in the Microsoft 365 Admin Center:

1. Bug Report - Intermittent Failure When Adding Members: Over the past few months, adding a member to a Shared Mailbox frequently fails on the first attempt (the UI either shows an error or does not save the change). Administrators have to repeat the exact same action a second time for the member to be successfully added. Please investigate this stability/caching issue.

2. Feature Request - Bulk Assign Shared Mailboxes per User: Currently, adding a single user to multiple Shared Mailboxes requires opening each mailbox individually. Please add a feature under "Active Users" > [User Profile] > "Mail" tab (similar to "Manage groups") that allows administrators to select one user and bulk-assign them to multiple Shared Mailboxes at once.

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2 answers

Your answer

Answer 1

Hello @Erick

Since this is a user-to-user community forum, I can only provide guidance and troubleshooting suggestions based on my experience as a user and the information you have shared.

From what you have described, I understand that you have been unable to save the changes when adding members to a shared mailbox, and the issue has persisted for the past few weeks.

As an initial troubleshooting step, I recommend clearing your browser cache and cookies, signing in again, and checking whether you can add the members successfully. It would also be helpful to test using a different browser or device to determine whether the issue is related to the current browser session or environment.

If you are using a Mac and using Safari browser, you can try with Microsoft Edge or Google Chrome to compare the behavior. If permitted by your organization’s policies, you can also test after temporarily disconnecting from a VPN or proxy to rule out possible connectivity-related interference.

If the issue continues, I recommend collecting the following information before escalating the case:

A screenshot of the error or what happens when you try to save the changes.
The troubleshooting steps you have already completed, such as clearing the cache, testing another browser or device, or testing without a VPN.
Whether the issue occurs with one specific shared mailbox or multiple shared mailboxes.
Whether another administrator experiences the same behavior.
The approximate date when the issue first started.

Since this behavior has continued for the past few weeks, if the troubleshooting above does not resolve the issue, I would recommend creating a support request with Microsoft Support. Their support engineers can investigate the issue more closely, collect and analyze relevant diagnostic information or logs, and, if necessary, escalate the case to the appropriate back-end or engineering team for further investigation.

As an administrator, you can submit a support request by following the instructions here: Get support - Microsoft 365 admin | Microsoft Learn

For bulk assigning a user to multiple shared mailboxes, you can follow the steps provided in the AI response using the Exchange admin center (EAC). The process should be similar to what is shown in the screenshot below.

I hope these suggestions help you narrow down the issue. Please give them a try and let me know if you have any updates or if the issue continues.

Answer 2

The Exchange admin center already supports assigning one user to multiple shared mailboxes in one operation: select the shared mailboxes under Recipients > Mailboxes, then use Mailbox delegation to add that user.

Bulk-assign the user in the Exchange admin center

Open Microsoft 365 admin center > Admin centers > Exchange.
In the Exchange admin center, select Recipients > Mailboxes.
Select all shared mailboxes to which the user needs access.
Select Mailbox delegation.
Under Add a delegate, enter the user’s name or email address.
Under Select permission types, choose:
- Full access — allows the user to open and manage mailbox contents.
- Send as — allows messages to appear as though they came directly from the shared mailbox.
- Send on behalf — identifies the user as sending on behalf of the mailbox.
Select Save.

Microsoft documents this multi-mailbox workflow directly in the EAC.^1^

This addresses the bulk-assignment requirement, although it is mailbox-oriented rather than located under Active users > user profile. Submit the requested user-oriented UI enhancement through the Feedback button at the bottom of the Microsoft 365 admin center; that form is Microsoft’s documented channel for admin-center bugs and feature enhancements.^2^

PowerShell alternative

For repeatable assignments, connect to Exchange Online PowerShell and apply permissions to a mailbox list. Access is controlled by Exchange Online RBAC, so the signed-in account must have the necessary mailbox-permission role.^3^

Connect-ExchangeOnline

$user = "[Email]"
$mailboxes = "[Email]", "[Email]"

foreach ($mailbox in $mailboxes) {
    Add-MailboxPermission -Identity $mailbox -User $user `
        -AccessRights FullAccess -InheritanceType All
    Add-RecipientPermission -Identity $mailbox -Trustee $user `
        -AccessRights SendAs -Confirm:$false
}

Add-MailboxPermission grants Full Access; Add-RecipientPermission grants Send As. These are distinct permissions—Full Access alone does not permit sending from the mailbox.^1^

Verify the assignments:

foreach ($mailbox in $mailboxes) {
    Get-MailboxPermission -Identity $mailbox |
        Where-Object User -Like $user
    Get-RecipientPermission -Identity $mailbox -Trustee $user
}

Disconnect-ExchangeOnline -Confirm:$false

Report the intermittent first-save failure

There is no confirmed current Microsoft-known issue in the available public information that exactly matches a first-attempt failure when saving shared-mailbox membership. The documented Microsoft 365 admin-center operation is still:

Teams & groups > Shared mailboxes > select mailbox > Members > Edit > Add members > Save.^4^

Because the failure is intermittent:

Go to Microsoft 365 admin center > Health > Service health.
Review Exchange Online incidents and advisories, including Issue history.
If no relevant issue appears, select Report an issue on the Service health page. This lets Microsoft correlate reports across tenants.^5^
Also submit the bug using the admin center’s bottom-of-page Feedback button.
If it continues, open Help & support, describe the issue, and select Contact Support. Microsoft recommends separate support requests for separate issues.^6^

Include the UTC timestamp, affected shared mailbox and user, browser, exact UI path, displayed error text, whether the second identical save succeeds, and how frequently it occurs. Avoid posting tenant identifiers or user details in a public forum.

References