How to create a shared mailbox in Microsoft 365: admin center, PowerShell and converting a user mailbox

Creating a shared mailbox in Microsoft 365 takes an Exchange admin about two minutes in the admin center, and one line in PowerShell. The settings that decide whether the team can use it well, Sent Items, permissions and sign-in, take another five. This guide covers all of it, including the case where the mailbox already exists as a departing employee's account.

How do you create a shared mailbox in Office 365?

Office 365 is now Microsoft 365, and the admin center is the same. You need the Exchange admin role; if the Shared mailboxes page says you do not have permission, you are not an admin. Your subscription also has to include Exchange Online. Microsoft 365 Apps for business does not; Business Basic, Standard and Premium do.

Before creating, decide whether a shared mailbox is the right object. It is for several people answering one address. A distribution list is for broadcasting, and a Microsoft 365 group is for mail plus files and Teams. Shared mailbox vs distribution list vs Microsoft 365 group works through the choice. Microsoft notes that a shared mailbox cannot be migrated to a group later.

Create a shared mailbox in the Microsoft 365 admin center

• Sign in to the admin center as a user with the Exchange admin role.
• Go to Teams & groups > Shared mailboxes. If Teams & groups is not in the left pane, select Show all.
• Select Add a shared mailbox. Enter a name; the email address is generated from it and can be edited.
• Select Save changes. Microsoft notes it may take a few minutes before members can be added.
• Under Next steps, select Add members to this mailbox, then Add members. Pick the people who should read and reply, select Add, and close.

Every new shared mailbox is created with sign-in blocked, and it should stay that way. The mailbox has a user account with a system-generated password that nobody is meant to know. Steps verified October 2026 on Create a shared mailbox.

If the name is already an address in your tenant, creation fails with an error that the proxy address is already being used. Create the mailbox under a different name and rename it afterward from the Shared mailboxes page.

Create a shared mailbox in the Exchange admin center

The Exchange admin center at admin.exchange.microsoft.com gives the same result with explicit control over permissions, which the Microsoft 365 admin center bundles behind the word members.

• Go to Recipients > Mailboxes and select Add a shared mailbox.
• Fill in Display name, Email address and Alias, then select Create.
• Under Next steps, select Add users to this mailbox, then Add users, pick the people, and save.
• To adjust later, select the mailbox and choose Manage mailbox delegation. Edit next to Read and manage (Full Access) or Send As adds or removes people.

Microsoft's note on that page is the one to remember. Full Access lets a user open the mailbox, Send As lets them send from it, and both are required for successful shared mailbox operation. Send on Behalf is set in PowerShell. Source: Shared mailboxes in Exchange Online. Hybrid Exchange organizations should create shared mailboxes in the on-premises Exchange admin center instead.

Create a shared mailbox with PowerShell

Connect first with Connect-ExchangeOnline from the Exchange Online PowerShell module. Then, following Microsoft's own example on the page above:

• New-Mailbox -Shared -Name 'Sales Department' -DisplayName 'Sales Department' -Alias Sales
• Add-MailboxPermission -Identity Sales -User priya@yourcompany.com -AccessRights FullAccess -InheritanceType All
• Add-RecipientPermission -Identity Sales -AccessRights SendAs -Trustee priya@yourcompany.com
• Set-Mailbox -Identity Sales -GrantSendOnBehalfTo priya@yourcompany.com (only if you want Send on Behalf instead of Send As)

Microsoft's example grants Full Access and Send on Behalf to a mail-enabled security group in one pipeline. That is efficient for a large team, with one catch. Automapping, the feature that makes the mailbox appear in Outlook automatically, only works when Full Access is granted to a user by name. If you grant through a group, members add the mailbox manually using how to add a shared mailbox in Outlook.

To set a specific address rather than the default domain, include -PrimarySmtpAddress sales@yourcompany.com. Microsoft's distribution list conversion example uses it.

Convert a user mailbox to a shared mailbox

When someone leaves and the team needs their client history, convert the mailbox instead of forwarding it. All mail and calendar items stay, and so do the inbox rules. Steps verified October 2026 on Convert a user mailbox to a shared mailbox.

• The mailbox must have a license at the moment of conversion, or the option does not appear. If you already removed it, add it back.
• In the admin center go to Users > Active users, select the user, open the Mail tab, select Convert to shared mailbox and then Convert.
• If the mailbox is under 50 GB, remove the license from the account and stop paying for it. Over 50 GB, either trim it or assign Exchange Online Plan 2.
• Do not delete the user account. The shared mailbox is anchored to it. If the account was already deleted, restore it, assign a license, reset the password, wait up to 24 hours for the mailbox to be re-created, then convert.
• Reset the password or block sign-in. Microsoft is explicit that the original username and password keep working on the shared mailbox after conversion unless you do.
• Add the team as members, and remove any forwarding the former employee had set up.

Converting back is done in the Exchange admin center: Recipients > Mailboxes, select the mailbox, Others tab, Convert to regular mailbox, Confirm. Then assign a license and reset the password in the Microsoft 365 admin center.

Convert a distribution list to a shared mailbox

There is no automated conversion. Microsoft's procedure: record the list's members and properties, then free its email address or delete the list. Create a shared mailbox with the same address and display name, and re-add the members with Full Access and Send As. Then ask everyone to remove the old autocomplete entry in Outlook.

The full PowerShell sequence is on the conversion page linked above. Plan it for a quiet hour; between deleting the list and creating the mailbox, mail to that address bounces.

Three settings to change before the team starts

• Sent items. On the shared mailbox page in the admin center, select Edit under Sent items and turn on copies for items sent as and on behalf of the mailbox. Or run Set-Mailbox support@yourcompany.com -MessageCopyForSentAsEnabled $true and the same with -MessageCopyForSendOnBehalfEnabled. Without this, every reply disappears into the sender's personal folder; how to send email from a shared mailbox explains why.
• Automatic replies. Edit under Automatic replies lets you set a text-only reply for internal and external senders. Use it to state a response time.
• Show in global address list. Leave it on. Hiding the mailbox stops new members from adding it to their Outlook profile and breaks Send As in the Outlook desktop client.

The storage, member and licensing ceilings you will meet later are in shared mailbox limits, licensing and best practices.

What the mailbox will not do once it exists

The mailbox is a container, and a good one for a front desk. It shows five people the same messages and lets them answer from one address. It has no owner field, no place for a note to a colleague, and no record that a client was promised a revised quote by Friday.

Teams add those on top with categories and willpower, and every setting that helps is a per-mailbox change for an admin to make.

We build Sektra, a separate shared inbox workspace that syncs two-way with Microsoft 365, shared mailboxes included. The mailbox you just created stays in Microsoft 365. Sektra connects to it with a member account through Microsoft sign-in, and never sees that password. It adds an owner per thread, internal notes, assignment and the memory layer, the record Sektra builds per contact of commitments made and questions left open.

Setup is on the Outlook integration page and in connect an Outlook shared mailbox. The reasoning is in where an Outlook shared mailbox stops. Founders setting up a first support@ or hello@ address for a small team can start at Sektra for founders.