How to Create and Manage Shared Mailboxes in Microsoft 365

Shared mailboxes are one of the most commonly used features in Exchange Online. They allow multiple users to read, send from, and manage a single email address — ideal for addresses like info@, support@, billing@, or sales@. Unlike distribution lists, shared mailboxes store email and allow replies, making them suitable for teams that actively manage inbound correspondence.

Shared mailboxes in Microsoft 365 do not require a licence for the mailbox itself, up to 50GB of storage. Users who access the shared mailbox must have a valid Microsoft 365 licence of their own.

Creating a Shared Mailbox

There are two ways to create shared mailboxes: through the main Microsoft 365 Admin Centre and through the Exchange Admin Centre. The Admin Centre method is simpler for most administrators.

Via the Microsoft 365 Admin Centre

1. Navigate to admin.microsoft.com and sign in as a Global Administrator or Exchange Administrator.
2. In the left-hand navigation, go to Teams and Groups, then Shared Mailboxes.
3. Select Add a shared mailbox.
4. Enter a display name (what appears in the From field when sending) and an email address. The address must use one of your verified domains.
5. Select Save changes. The mailbox is created immediately.
6. You will then be prompted to add members. These are the users who will have access to the mailbox.

Via the Exchange Admin Centre

For more granular options, use the Exchange Admin Centre at admin.exchange.microsoft.com. Navigate to Recipients, then Mailboxes, and select Add a shared mailbox. The Exchange Admin Centre provides additional options during creation and easier access to advanced settings afterwards.

Configuring Permissions

Shared mailboxes use three primary permission types. Understanding the difference between them is important for correct configuration.

Full Access

Full Access allows a user to open the shared mailbox, read its contents, and manage mail within it. Users with Full Access can delete messages, create folders, and organise the inbox. Full Access does not grant the ability to send email. This permission is what enables automapping — the shared mailbox appearing automatically in Outlook.

Send As

Send As allows a user to compose and send email that appears to come from the shared mailbox address. The recipient sees only the shared mailbox address in the From field, not the individual user's address. This is the appropriate permission for most shared mailboxes.

Send on Behalf

Send on Behalf displays both the shared mailbox address and the individual user's address in the From field, formatted as "User Name on behalf of Shared Mailbox Name." This is useful in situations where transparency about which team member sent the message is required, but it is less common than Send As for customer-facing shared addresses.

Automapping in Outlook

When a user is granted Full Access to a shared mailbox, Exchange Online automatically adds it to their Outlook profile the next time Outlook connects to Exchange. This is called automapping and it is enabled by default.

Automapping is convenient but can cause problems in organisations where users have access to many shared mailboxes — loading dozens of mailboxes on startup slows Outlook significantly. To grant Full Access without enabling automapping, use PowerShell:

Users can then add the shared mailbox manually in Outlook by going to File, then Account Settings, then Account Settings, selecting their Exchange account, clicking Change, then More Settings, then Advanced, and adding the shared mailbox name.

Mailbox Policies and Settings

Retention Policies

Apply a retention policy to the shared mailbox to manage how long email is kept. In the Microsoft Purview compliance portal, assign an appropriate retention policy based on your organisation's data retention requirements and any regulatory obligations.

Out of Office Auto-Replies

Configure automatic replies for shared mailboxes via PowerShell or the Outlook web app when signed in as the shared mailbox. Auto-replies are useful for support or info addresses that operate during business hours only.

Email Forwarding

Shared mailboxes can forward copies of received email to individual mailboxes. Configure forwarding cautiously — it can create unexpected mail loops and may conflict with your anti-spam policies.

Accessing Shared Mailboxes on Mobile

Shared mailboxes do not automatically appear in the Outlook mobile app. Users must add them manually. In Outlook for iOS or Android, go to Settings, select the user's account, then tap Add a Shared Mailbox. Enter the shared mailbox email address and it will be added as a separate account in the app.

Converting a User Mailbox to a Shared Mailbox

When an employee leaves, you may want to convert their mailbox to a shared mailbox so the team can access historical correspondence without keeping the user account active and consuming a licence. This is a common offboarding step.

1. In the Microsoft 365 Admin Centre, go to Active Users and block sign-in for the departing user account.
2. Navigate to Teams and Groups, then Shared Mailboxes, and select Add a shared mailbox. Alternatively, in the Exchange Admin Centre, open the user's mailbox and use the Convert option.
3. After conversion, the user's licence can be removed. The mailbox retains its contents and remains accessible to whichever users you grant Full Access.
4. Set up an auto-reply notifying senders of any change in contact information.