Introduction
Shared Mailboxes are a staple of Microsoft 365 environments, allowing multiple users to manage a single address (like [email protected]) without requiring a dedicated license or sharing passwords. By default, when an administrator grants a user “Full Access” permissions to a Shared Mailbox, Microsoft 365 automatically maps that mailbox into the user’s Outlook client. This feature, known as Auto-Mapping, is usually helpful, but it can cause severe performance issues if a user has access to dozens of large mailboxes. This guide explains how to manage, disable, and re-enable Auto-Mapping using Exchange Online PowerShell.
Prerequisites
You cannot configure Auto-Mapping from the Microsoft 365 Admin Center or the Exchange Admin Center GUI. It must be done via PowerShell. You need Exchange Administrator privileges and the Exchange Online PowerShell V3 module installed on your management machine.
Step 1: Connect to Exchange Online
Open an elevated PowerShell prompt and connect to your tenant:
Connect-ExchangeOnline -UserPrincipalName [email protected]
Authenticate using your credentials and Multi-Factor Authentication (MFA) when prompted.
Step 2: Disable Auto-Mapping When Granting Access
If you are assigning Full Access to a new user and want to prevent the mailbox from automatically appearing in their Outlook, you must append the -AutoMapping $false parameter to the standard permissions command.
To grant John Doe access to the Sales mailbox without auto-mapping:
Add-MailboxPermission -Identity "[email protected]" -User "[email protected]" -AccessRights FullAccess -AutoMapping $false
John will now have access, but he must manually add the Shared Mailbox via File > Account Settings > Advanced > Open these additional mailboxes in Outlook. This prevents his Outlook client from constantly syncing the Sales data unless he explicitly asks it to.
Step 3: Remove Auto-Mapping from an Existing Permission
If a user already has Full Access and the mailbox is causing Outlook to freeze or crash, you cannot simply run a command to “turn off” auto-mapping. You must remove the Full Access permission entirely, and then immediately re-add it with the $false flag.
First, remove the permission:
Remove-MailboxPermission -Identity "[email protected]" -User "[email protected]" -AccessRights FullAccess -Confirm:$false
Second, wait a few moments, then re-add it without auto-mapping:
Add-MailboxPermission -Identity "[email protected]" -User "[email protected]" -AccessRights FullAccess -AutoMapping $false
Step 4: Re-Enable Auto-Mapping
If a user decides they actually want the mailbox to appear automatically in their folder pane, you repeat the same removal and re-addition process, but change the flag to $true.
Remove-MailboxPermission -Identity "[email protected]" -User "[email protected]" -AccessRights FullAccess -Confirm:$false
Add-MailboxPermission -Identity "[email protected]" -User "[email protected]" -AccessRights FullAccess -AutoMapping $true
Note: Auto-mapping relies on Autodiscover. It can take anywhere from 15 minutes to a few hours for the Shared Mailbox to physically appear or disappear from the Outlook desktop client after running these commands.