Calendar Problems

How to Stop Unwanted Outlook Calendar Notifications from a Shared Mailbox

Maira Mehtab Sep 27, 2026 869 views

Question details

Users need to stop unexpected calendar notifications that are automatically sent to staff from a shared mailbox when meetings are booked or joined.

Product: Microsoft Outlook
Device & OS: not provided
Scenario: Staff members are receiving unwanted meeting notifications or updates originating from a shared mailbox, which often previously belonged to a former user.
Observed behavior: Unexpected notification emails are sent on behalf of a shared mailbox when calendar events are created, updated, or joined.

Before you start

Ensure you have Microsoft 365 administrator privileges, as you will need access to the Exchange Admin Center or Exchange Online PowerShell to check and modify mailbox permissions.

Solution 1Recommended

Adjust Calendar Delegate and Folder Permissions

Check and modify the delegate or folder permissions of the shared mailbox to prevent it from automatically sending notifications on behalf of the calendar owner.

Hidden delegate configurations are the most common cause of unwanted calendar notifications. By resetting these permissions, you can stop the automated emails.

Check current permissions

Identify the specific account sending the notifications and review its permissions on the owner's calendar.

Reduce or remove permissions

If the shared mailbox account has 'Editor' permissions on the calendar, remove this access or reduce it to 'Reviewer', then test again.

Refresh hidden delegates

If no delegate is currently configured in the settings, temporarily add the account as a delegate, save the changes, and then remove the permission. This forces the backend configuration to refresh and clear hidden glitches.

Former User Accounts: If the shared mailbox belonged to a former user, converting it temporarily back to a user mailbox might allow you to log in, manually clear inbox rules, and then convert it back.

Solution 2

Verify Permissions Using Exchange Online PowerShell

Use PowerShell commands to accurately verify the hidden calendar permissions that might not be visible in the standard Outlook interface.

Solution 3

Open a Microsoft 365 Support Request

If permissions and rules appear normal but the notifications persist, advanced backend diagnostics by a Microsoft engineer are required.

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Frequently Asked Questions

Why is a shared mailbox sending calendar notifications?

This usually happens because the shared mailbox still retains hidden delegate permissions or Editor rights on a user's calendar, causing it to automatically send meeting updates on behalf of the owner.

Can I fix hidden calendar rules by converting the shared mailbox back to a user mailbox?

Yes, temporarily converting the shared mailbox back to a standard user mailbox can sometimes allow an administrator to log into the account directly, clear hidden Inbox rules or delegate settings, and then convert it back safely.

What PowerShell command checks calendar folder permissions?

You can use the 'Get-MailboxFolderPermission -Identity owner@example.com:\Calendar -User sharedmailbox@example.com' command in Exchange Online PowerShell to view the exact permissions assigned to the shared mailbox.

Outlook & Email Problems