Shared mailboxes in Outlook and Microsoft 365: the complete guide
A shared mailbox (often called a shared inbox) lets a team read, reply to and send email from one address, such as support@ or info@, inside Outlook. This guide covers how to create one in Microsoft 365, which permissions to grant, how to add it to every version of Outlook, how to fix the most common problems, and where its limits are.
What is a shared mailbox in Outlook and Microsoft 365?
A shared mailbox is a mailbox in Exchange Online with its own email address, inbox, folders, Sent Items and calendar. Instead of one person owning it, a group of people in your organization are given permission to open it in Outlook and work from it together. When someone replies, the email comes from the shared address, not from their personal one.
Shared mailboxes are the standard way to run team addresses in Microsoft 365, for example:
- Customer support and service (support@, help@)
- General enquiries (info@, contact@)
- Sales, quoting and orders (sales@, orders@)
- Internal service desks like IT, HR, finance and accounts payable
People search for this as both "shared mailbox" and "shared inbox." In Microsoft 365 they usually mean the same thing: shared mailbox is Microsoft's term, and shared inbox is the everyday one.
Shared mailbox vs Microsoft 365 group vs distribution list
Microsoft 365 offers three ways to give a team one address. They behave very differently, and choosing the wrong one is a common source of missed and duplicate replies.
| Shared mailbox | Microsoft 365 group | Distribution list | |
|---|---|---|---|
| Has its own inbox | Yes | Yes, as group conversations | No, it forwards to members |
| Replies come from | The shared address | The group address | Each member's own address |
| Shared calendar | Yes | Yes | No |
| External members | No | Yes, as guests | Yes, as contacts |
| Can stop members deleting mail | No | Yes | Not applicable |
| Best for | Team addresses like support@ that people reply from | Collaboration that also uses Teams and SharePoint | Announcements and notifications |
If your team currently uses a distribution list, see distribution group vs shared mailbox and how to convert a distribution list to a shared mailbox.
Shared mailbox limits and licensing at a glance
These figures come from Microsoft's documentation on shared mailboxes in Microsoft 365.
| Item | What Microsoft says |
|---|---|
| Storage without a license | Up to 50 GB |
| Storage with a license | Up to 100 GB with an Exchange Online Plan 2 license |
| Archiving and litigation hold | Need Exchange Online Plan 2, or Plan 1 with Exchange Online Archiving |
| User licenses | Every person using it needs their own licensed Exchange Online mailbox |
| External access | Not possible; members must be in your organization |
| Sign-in | Blocked by default; the shared account isn't meant to be signed in to |
| Encryption | Email sent from a shared mailbox can't be encrypted |
| Deleting messages | You can't prevent members from deleting messages |
| What happens when it's full | It stops sending, then stops receiving and senders get a bounce |
For more on staying under the storage limit, see managing storage in Microsoft 365 shared mailboxes.
How to create a shared mailbox in Microsoft 365
You need an Exchange admin role, or a Global Admin, to create a shared mailbox.
In the Microsoft 365 admin center
- Sign in to the Microsoft 365 admin center.
- Go to Teams & groups > Shared mailboxes. If you don't see Teams & groups, select Show all.
- Select + Add a shared mailbox, enter a name and check the email address it creates.
- Select Save changes. It can take a few minutes before you can add members.
- Under Next steps, select Add members to this mailbox, choose the people who will work from it, then select Add.
Members added here get Full Access and Send As permissions. Sign-in for the shared mailbox's own account is blocked automatically.
With Exchange Online PowerShell
PowerShell is faster when you're creating several mailboxes or adding many members. This creates the mailbox, gives one person Full Access and Send As, and makes sent mail save to the shared mailbox:
Connect-ExchangeOnline New-Mailbox -Shared -Name "Support" -DisplayName "Support" -PrimarySmtpAddress [email protected] Add-MailboxPermission -Identity [email protected] -User [email protected] -AccessRights FullAccess -InheritanceType All Add-RecipientPermission -Identity [email protected] -Trustee [email protected] -AccessRights SendAs -Confirm:$false Set-Mailbox -Identity [email protected] -MessageCopyForSentAsEnabled $true -MessageCopyForSendOnBehalfEnabled $true
Repeat the two permission lines for each member. Before you create anything, how IT teams should structure shared mailboxes covers the naming and structure decisions worth making first.
Which permissions should members have?
| Permission | What it allows | What recipients see |
|---|---|---|
| Full Access | Open the mailbox, read, move, delete and organize mail, use the calendar. Can't send on its own. | Nothing; it doesn't allow sending |
| Send As | Send email that appears to come from the shared mailbox | "Support" |
| Send on Behalf | Send email on behalf of the shared mailbox | "Alex on behalf of Support" |
For a team address, give each member Full Access and Send As. Microsoft notes both are needed for the mailbox to work properly, and Send As gives customers a consistent reply from the team address. Use Send on Behalf only when you want customers to see who replied.
Grant permissions to each person directly rather than through a security group. Microsoft's documentation notes that automapping, which makes the mailbox appear in Outlook automatically, doesn't work when access is given through a security group. For a deeper look at who should get access and how to review it, see shared mailbox ownership and access best practices.
How to add a shared mailbox to Outlook
Once someone has Full Access, how they open the mailbox depends on which Outlook they use. These steps follow Microsoft's guide to opening and using a shared mailbox in Outlook.
New Outlook for Windows
- Close and reopen Outlook. The shared mailbox should appear in the folder pane under Shared with me.
- If it doesn't, select Mail, right-click your account name in the folder pane and choose Add shared folder or mailbox.
- Enter the shared mailbox address, such as [email protected].
Classic Outlook for Windows
- Close and reopen Outlook. With automapping on, the shared mailbox appears in the folder pane automatically.
- If it doesn't, go to File > Account Settings > Account Settings.
- On the Email tab, select your account and choose Change, then More Settings > Advanced > Add.
- Enter the shared mailbox address and select OK, then Next > Finish, and restart Outlook.
Outlook on the web
- Right-click Folders in the left pane and choose Add shared folder or mailbox.
- Enter the shared mailbox address and select Add.
- To work from it in its own browser tab, select your profile picture, choose Open another mailbox and enter the address.
Outlook for Mac
- Go to Tools > Accounts and add the shared mailbox as an Exchange account, entering the shared address in the E-mail address field.
- Under Authentication, sign in with your own credentials, and turn on Sync shared mailbox.
Outlook for Mac doesn't automap shared mailboxes and supports Full Access only. You also need Send As or Send on Behalf permission to send from it.
Outlook mobile (iOS and Android)
- Sign in to your own account in the Outlook app.
- Tap Add Account, then Add a Shared Mailbox, and choose the account that has access.
Both your mailbox and the shared mailbox must be in Exchange Online.
Sending from the shared mailbox
When you reply to a message in the shared mailbox, Outlook usually fills in the shared address automatically. For a new message, show the From field (in new Outlook and Outlook on the web, open the options and choose Show From), then pick the shared address. Always check the From field before sending, so customers don't get a reply from your personal address.
Make sent emails save to the shared mailbox
By default, depending on your settings and Outlook version, replies sent from a shared mailbox can land only in the sender's own Sent Items. The rest of the team then can't see what was said. An admin can fix this:
- In the Microsoft 365 admin center, go to Teams & groups > Shared mailboxes and select the mailbox.
- In the Sent items section, select Edit.
- Turn on Copy items sent as this mailbox and Copy items sent on behalf of this mailbox, then save.
The change applies to new messages only and can take a little while to take effect. The sender keeps a copy in their own Sent Items too.
Set up automatic replies
Only an admin can set automatic replies for a shared mailbox. In the admin center, go to Teams & groups > Shared mailboxes, select the mailbox, then Automatic replies > Edit. Turn them on, choose whether they go to people inside your organization, outside it or both, write the message and save.
Best practices to set up on day one
- Keep sign-in blocked on the shared mailbox's account. People should open it with their own credentials, never a shared password.
- Grant Full Access and Send As to each person directly, so automapping works and everyone can reply from the team address.
- Turn on both Sent Items copy settings before the team starts replying.
- Use a clear name and address that describes the work, like orders@ or billing@, not a person's name.
- Plan for storage early. Set up archiving or a retention approach before the mailbox gets close to 50 GB.
- Decide how ownership will work before volume grows. Outlook won't show who is handling a message, so agree on a system from the start. Best practices for high-volume shared mailboxes covers the habits that scale.
Troubleshooting common shared mailbox problems
The shared mailbox doesn't appear in Outlook. Restart Outlook and give it some time; new permissions can take a while to replicate. Check that the person was given Full Access directly, not through a security group, or automapping won't add it. In new Outlook, look under Shared with me. If it still doesn't appear, add it manually using the steps above.
"You do not have the permission to send the message on behalf of the specified user." If the mailbox or permission is new, Microsoft says this is usually replication delay that clears in about an hour. If it persists, check that the person has Send As or Send on Behalf, not just Full Access.
Send As doesn't work in classic Outlook. Send As and Send on Behalf don't work in the Outlook desktop app if the shared mailbox is hidden from the address list. Unhide it from the global address list.
"The proxy address is already being used." Another mailbox already uses that address or alias. Create the mailbox with a different name, then rename it, or create it in Exchange Online PowerShell.
The mailbox stopped sending or receiving. It has probably reached its storage limit. Archive or delete old mail, or license the mailbox for more space.
Where shared mailboxes fall short
A shared mailbox gives a team shared access to email, but not a way to manage the work inside it. Outlook has no way to assign an email to one person, no response-time tracking or SLA alerts, no reporting on workload, and no status for open, waiting or done. As volume grows, the result is missed emails and duplicate replies. We cover all eight gaps in Outlook shared mailbox limitations and how to fix them, and the broader discipline in what is shared mailbox management?
Adding structure without leaving Outlook
Most teams don't need to replace their shared mailbox to fix those gaps. Emailgistics works on top of the shared mailboxes you already have, as an add-in inside Outlook:
- Collision-free by design. Every email is routed to exactly one owner, so two people can't end up replying to the same message. Reassign anytime and ownership moves with it. See how to assign emails in an Outlook shared mailbox.
- SLA tracking and alerts warn the team before a reply is late.
- Live dashboards and reports show response times, workload and backlog.
- Internal notes and conversation history keep context with the email.
Your email stays in Exchange Online and your team keeps working in Outlook. For IT, the Microsoft 365 integration overview covers what gets installed, where data lives and how to remove it. For a side-by-side view, see Emailgistics vs a shared mailbox alone.
To see it with your own shared mailbox, book a demo and start a 14-day free trial, no credit card required.
Ask your Microsoft 365 admin to give you Full Access and Send As permissions on the shared mailbox. In most organizations the mailbox then appears in classic Outlook and new Outlook automatically after you restart. If it doesn't, right-click your account name in the folder pane and choose Add shared folder or mailbox in new Outlook or Outlook on the web, or use File, Account Settings, More Settings, Advanced, Add in classic Outlook. On iOS and Android, tap Add Account, then Add a Shared Mailbox.
No, not under 50 GB. A shared mailbox can store up to 50 GB without its own license, but every person who uses it needs a licensed Exchange Online mailbox of their own. The shared mailbox needs an Exchange Online Plan 2 license if it grows past 50 GB, and an Exchange Online Plan 2 or Exchange Online Archiving license for in-place archiving or litigation hold.
In Microsoft 365 they usually mean the same thing. Shared mailbox is Microsoft's term for a mailbox with its own address that several people can read and send from. Shared inbox is the more general term people use for any inbox a team works from together, including shared inbox software that runs on top of a shared mailbox.
Depending on your settings and Outlook version, replies sent from a shared mailbox can be saved only to the sender's own Sent Items. An admin can fix this in the Microsoft 365 admin center by opening the shared mailbox, editing Sent items and turning on both Copy items sent as this mailbox and Copy items sent on behalf of this mailbox. The change applies to new messages only.
No. Only people inside your organization can be given access to a shared mailbox. If you need to include external people, Microsoft suggests using a Microsoft 365 group instead.
Not natively. Outlook has no way to make one person the owner of a message in a shared mailbox, so teams fall back on categories, flags or folders. Tools like Emailgistics add real assignment inside Outlook, routing every email to exactly one owner so two people never work the same message.