Convert a Microsoft 365 user mailbox to a shared mailbox

SUPPORTED TENANTPILOT TASK · Fictional examples · Updated October 2026

What conversion changes

Conversion changes the mailbox type, not the message history. It does not automatically grant colleagues access, remove licences, preserve records indefinitely or finish an employee-leaver process.

Checks before making changes

• Do not delete the original user account: Microsoft requires it to anchor the shared mailbox. Block sign-in appropriately for leavers.
• Confirm approval, the mailbox identity, its retention requirements and any applicable hold.
• Check licensing before removal. Shared mailboxes can require licences in some circumstances.
• Review sign-in restrictions, delegated access and any existing mailbox forwarding.

Convert in Exchange admin centre

1. Open Users → Active users in the Microsoft 365 admin centre.
2. Select the correct user and open the Mail tab.
3. Choose Convert to shared mailbox, then confirm the conversion.
4. Confirm the result and separately review access and licences.
5. Test access with an approved delegate.

PowerShell example

Set-Mailbox -Identity "[email protected]" -Type Shared

Use this only in the appropriate Exchange Online environment after checking any hybrid-directory dependencies.

Where TenantPilot fits

TenantPilot includes both Convert mailbox to shared and Convert shared mailbox to regular tasks. It does not replace the wider offboarding and compliance review.