Shared mailboxes with licences assigned alert

This article explains the Shared mailboxes with licences assigned alert in Sync 365, why it appears, and what to check before billing a customer.

This alert helps identify shared mailboxes that still have Microsoft 365 licences assigned. This commonly happens during user offboarding, where a user mailbox is converted to a shared mailbox but the licence is not removed.

Why this alert matters

Shared mailboxes often do not need a Microsoft 365 licence if they are used only as standard shared mailboxes and remain within Microsoft’s limits.

If a shared mailbox still has a paid licence assigned, the customer may be paying for a licence they no longer need.

This alert gives you a chance to review the mailbox before syncing billing or invoicing the customer.

Common causes

• A user left the business and their mailbox was converted to a shared mailbox.
• The Microsoft 365 licence was not removed after conversion.
• The mailbox still needs a licence for archive, compliance, or mailbox-size reasons.
• A licence was left assigned temporarily during migration or offboarding.
• The customer intentionally keeps the licence assigned for a specific feature.

How to review the alert

1. Open the affected company in Sync 365.
2. Review the shared mailbox alert or shared mailbox licence list.
3. Identify the shared mailbox and the licence assigned to it.
4. Check the mailbox in Microsoft 365 Admin Center or Exchange Admin Center.
5. Confirm whether the licence is still required.

When a shared mailbox may still need a licence

Some shared mailboxes may still need a licence depending on how they are used.

Examples include:

• The mailbox uses an archive mailbox.
• The mailbox exceeds Microsoft’s unlicensed shared mailbox size limits.
• The mailbox needs features that require a licence.
• The mailbox is being used in a way that does not fit normal shared mailbox usage.
• Your customer or compliance policy requires the licence to remain assigned.

If you are unsure whether a shared mailbox needs a licence, check Microsoft’s current shared mailbox licensing guidance and the customer’s requirements before removing it.

What to do if the licence is not needed

1. Remove the licence from the shared mailbox in Microsoft 365.
2. Wait for Microsoft and Sync 365 to refresh.
3. Confirm the shared mailbox no longer appears in the alert.
4. Confirm the billing quantity updates as expected.

What to do if the licence is still needed

If the shared mailbox legitimately needs a licence, you may not need to take action.

If you do not want the alert to continue appearing for that mailbox or licence type, review whether it should be excluded or handled through your normal billing process.

Impact on customer billing

If the shared mailbox has a paid licence assigned, it may be included in licence counts depending on your mapping and billing configuration.

Before removing a licence, confirm whether the customer should still be billed for it. Before billing the customer, confirm whether the shared mailbox licence is intentional.

Best practice for offboarding

• When converting a user mailbox to a shared mailbox, review whether the licence should be removed.
• Check shared mailbox alerts before customer billing runs.
• Document exceptions where shared mailboxes intentionally keep licences.
• Use Sync 365 alerts to catch missed offboarding cleanup.

When to contact support

Contact support if:

• The mailbox is no longer shared but still appears in the alert.
• The licence was removed but the alert still appears after refresh.
• The shared mailbox does not appear in Microsoft but appears in Sync 365.
• The billing quantity does not update after the licence is removed.
• You are unsure how the mailbox is being counted for billing.

When contacting support, include the company name, shared mailbox address, licence name, screenshot of the alert, and whether the licence has already been removed in Microsoft 365.

Related articles

• Unused and under-provisioned licence alerts
• Missing Billing Profile alerts
• License Mapping/Configuration Options
• Global License Exclusions