Microsoft 365 guide

How to Set Up a Shared Mailbox in Microsoft 365

By Gander Web · Checked against Microsoft's documentation on 9 October 2026 · 7 min read

Shared mailbox, group, alias or distribution list?

Microsoft 365 has four ways to give an address to more than one person. Picking the wrong one is the most common reason a shared inbox feels awkward later, and Microsoft says a shared mailbox can't be turned into a Microsoft 365 group afterwards.

Create the shared mailbox

1. Sign in at admin.cloud.microsoft with an account that has the Exchange admin or Global admin role.
2. Go to Teams & groups > Shared mailboxes. If you can't see Teams & groups, select Show all in the left menu.
3. Select + Add a shared mailbox and type a name such as Accounts. The email address fills in from the name; change it to the address you want and pick your domain.
4. Select Save changes. Microsoft notes it can take a few minutes before you can add members.
5. Under Next steps, select Add members to this mailbox, then Add members, choose the people and select Add.

Every new shared mailbox has sign-in blocked by default. Leave it that way. Nobody should log in to info@ with a password; people open it from their own account, so their multi-factor sign-in covers it and removing someone's access is one click when they leave.

Check the permissions

There are three permissions, and Microsoft is explicit that you need two of them for a shared mailbox to work properly:

• Full Access (shown as Read and manage in the Exchange admin centre) lets someone open the mailbox, read, move and delete mail and use its calendar. On its own it doesn't let them send.
• Send As makes a reply look like it came from the mailbox itself: Accounts <[email protected]>.
• Send on Behalf shows who sent it: Sam on behalf of Accounts. Useful when customers should see a name.

To check or change them, open the Exchange admin centre, go to Recipients > Mailboxes, select the shared mailbox and open its delegation settings. Each person should have Full Access plus either Send As or Send on Behalf.

Open it in Outlook

Classic Outlook for Windows adds the shared mailbox to the folder list by itself (Microsoft calls this automapping) after the person closes and reopens Outlook.

Outlook on the web and the new Outlook: right-click Folders (or your name) in the folder list, choose Add shared folder or mailbox and type the shared address. In the new Outlook you'll also find shared mailboxes under Settings > Accounts > Shared with me.

iPhone and Android: in the Outlook app, tap Add account in the left-hand menu, then Add a shared mailbox, and enter its address. Microsoft only supports shared mailboxes in the Outlook app, not in Apple Mail or Gmail.

On Business Basic you won't have desktop Outlook, so Outlook on the web and the phone app are the two to use. Here's why, and what to do if someone needs desktop Outlook.

Fix: the shared mailbox isn't showing in Outlook

Work down this list. In our experience the first two cover most cases.

1. Restart Outlook fully. Classic Outlook only picks up new shared mailboxes when it starts.
2. Check how access was given. Automapping only works when permission is granted to the person directly. If Full Access was given to a security group, classic Outlook won't add the mailbox automatically, so grant it to each person or add the mailbox by hand.
3. Using the new Outlook or Outlook on the web? Automapping doesn't apply there. Add it with Add shared folder or mailbox as above.
4. Just added? Permission changes can take a little while to reach Outlook. Try again later before changing anything else.
5. Is the mailbox hidden from the address list? Microsoft notes that Send As and Send on Behalf don't work in desktop Outlook when the mailbox is hidden from the global address list.

Fix: replies land in your own Sent Items

This is by design. When you send from a shared mailbox, Exchange Online saves the copy in your Sent Items, so the rest of the team can't see what was sent from info@. Turning on one setting fixes it:

1. In the admin centre, go to Teams & groups > Shared mailboxes and select the mailbox.
2. Find the Sent items section and select Edit.
3. Tick both boxes (copy items sent as this mailbox, and sent on behalf of it) and save.

Or in Exchange Online PowerShell:

Connect-ExchangeOnline
Set-Mailbox -Identity [email protected] -MessageCopyForSentAsEnabled $true -MessageCopyForSendOnBehalfEnabled $true

It only applies to mail sent after you change it. Older replies stay in each person's own Sent Items.

Size limits and licences

• A shared mailbox doesn't need a licence of its own, but it's limited to 50 GB without one. Everyone who opens it needs an Exchange Online licence, which Business Basic includes.
• Microsoft requires a licence on the shared mailbox (Exchange Online Plan 2, or Plan 1 with the Exchange Online Archiving add-on) if it goes over 50 GB, needs an archive, or is placed on litigation hold.
• Don't use a shared mailbox to keep copies of everyone's mail. Microsoft's terms prohibit using archive mailboxes to store mail for multiple people.

Turning a leaver's mailbox into a shared mailbox

When someone leaves, converting their mailbox to a shared mailbox keeps their email reachable without paying for a licence. In the admin centre go to Users > Active users, select the person and, on the Mail tab, choose Convert to shared mailbox. The mailbox must still be licensed while you convert it; once it's shared and under 50 GB you can remove the licence.

Check the size first. Business plan mailboxes went up to 100 GB in 2026, so a long-serving person's mailbox can now be over the 50 GB a shared mailbox gets for free. Our storage guide covers what to do with their OneDrive at the same time.

Questions

Related guides

Sources

1. Create a shared mailbox (Microsoft 365 admin)
2. Exchange Online limits
3. Messages sent from a shared mailbox aren't saved to the Sent Items folder
4. Convert a user mailbox to a shared mailbox
5. Supported accounts in new Outlook for Windows

We checked every limit, menu path and date in this guide against the sources above on 9 October 2026. Microsoft changes these often. If something here no longer matches what you see, tell us and we'll update it.