Microsoft 365 / Create a shared mailbox and grant Full Access and Send As
A shared mailbox lets several staff members handle mail sent to one business address. Creating the mailbox alone does not give every staff member permission to read and reply. Full Access and Send As or Send on Behalf permissions need to be granted separately according to the purpose.
Things to Decide Before Creating
- Address and Display Name: Decide the name and domain that will be shown to customers and check that it does not duplicate an existing address.
- Persons in Charge: Establish at least two operational managers and a handover procedure.
- Sending Method: Decide whether only the shared address will be shown to customers or if it will display the person in charge as 'Sent on behalf of'.
- Storage and capacity: Check the expected mail volume and retention requirements. Additional licenses may be required.
Check current requirements in Microsoft’s shared mailbox creation guide and licensing and limits guide. Keep the shared mailbox account itself blocked from direct login, and users access it with the permissions assigned to their individual accounts.
This article is based on cloud Exchange Online mailboxes. In a hybrid Exchange environment, on-premises procedures are required depending on the location of the original management, so do not create duplicates. The person in charge of creation needs appropriate permissions, such as an Exchange administrator, and each user must have an Exchange Online mailbox with a license. Also check the 50 GB limit for shared mailboxes without a separate license and the conditions for additional retention features.
For example, if two customer support staff handle a shared address, both can be given read and manage permissions, and Send As can be added for the person who will reply to customers using the shared address. Do not assume that external partner accounts can be delegated access in the same way.
Creating a shared mailbox
- Go to [Teams & Groups] → [Shared Mailboxes] in the Microsoft 365 admin center. Alternatively, you can create it in the Exchange admin center under [Recipients] → [Mailboxes].
- Select [Add a shared mailbox] and enter a display name and email address. Check the spelling of the address before saving.
- Once creation is complete, open member or delegate permissions settings. Add the people who will use it and assign the necessary permissions separately.
Understand Full Access, Send As, and Send on Behalf
| Permissions | What you can do | Points to separately check |
|---|---|---|
| Full Access (read and manage) | Open the shared mailbox and manage mail and calendar | You cannot send as the shared address with this permission alone. |
| Send As | Send as if the shared mailbox sent it | This is a method where the recipient does not see the name of the person in charge. |
| Send on Behalf | The person in charge sends on behalf of a shared mailbox | The recipient may see the name of the person who sent on behalf. |
Microsoft distinguishes these three permissions in Exchange Online recipient permissions. The 'Read and Manage' option on the actual screen may correspond to full access in Exchange.
The order of granting Read and Send As separately
- In Exchange Admin Center → Recipients → Mailboxes, select a new shared mailbox. Compare the display name with the actual address.
- Open Mailbox permissions → Manage mailbox delegation (or Mailbox delegation, depending on the screen), then select Read and manage (Full Access). Add the person in charge, save, and then check the list again.
- Open Send As separately and add the users who should send from the shared address. A name in the Full Access list does not automatically mean that the same user has sending permission.
- Compare the two lists with the requested permission table. If recipients need to see a named employee sending on behalf of the shared mailbox, review 'Send on Behalf', but note that this item may not be available on the screen in shared mailboxes, so check the official Exchange Online PowerShell management documentation.
- Check the login block status of accounts connected to the shared mailbox in the active users section of the Microsoft 365 admin center. Do not unblock the shared account’s sign-in or share its password as a workaround when the mailbox does not open in Outlook.
If 'Send As' and 'Send on Behalf' are granted to the same person, 'Send As' takes precedence. Decide what indication the recipient needs and select only the necessary permission. This difference can be checked in the Microsoft recipient permission documentation above.
Test access, receiving, and sending
- Have the user with delegated permission sign in to Outlook with their own account and confirm that they can open the shared mailbox. If it does not appear automatically, the client may need to add the shared mailbox manually.
- Check reception by sending an email from an external test address to the shared address.
- Reply using an allowed sending method and verify whether the sender display matches the intention. It may take time for permissions to be applied.
In Outlook for the web, you can specify a shared address by selecting Open another mailbox from the user's profile menu. Automatic display in desktop Outlook is affected by full access directly granted to the user and conditions for automatic mapping. If permissions are granted through a group, automatic display may not occur, so distinguish between "not displayed" and "no access rights."
| Test | Results to be checked | Investigate if it fails |
|---|---|---|
| Open shared mailbox | Read inbox and perform necessary actions | Full access targets, permission propagation, client addition methods |
| Received externally | Test email arrives in the shared inbox | Address duplication · Domain · Message tracking |
| Reply from shared address | Display intended sender to external recipients | Send As · Send on behalf, choose sender, address-list visibility |
| Other person in charge can check the sending history | Sent mail can be checked from the agreed location | Set to save copies of sent items in the shared mailbox |
Also check sent mail and workflow rules
Even if sent from a shared address, if the copy remains only in the individual sent mailbox of the person in charge, it is difficult for other staff to verify if a reply has been made. In the Microsoft 365 admin center, go to Teams & groups → Shared mailboxes, select the mailbox, and choose Edit under Sent items. Record the existing options, select whether to keep copies for the sending methods you use, and save the change. Microsoft’s shared mailbox settings guide describes this location. You should send a test email to check both locations in practice.
For client-specific sent mail storage issues and server-side copy settings, refer to Resolving sent mail issues in Microsoft shared mailboxes. First identify the Outlook version and check the mailbox settings before considering a client registry change. For new Outlook, the documented workaround uses the server-side copy settings; the legacy registry workaround does not apply.
The operating rules specify the assignment of responsible personnel, marking processing as complete, and assigning responsibility for recovering mistakenly deleted emails. Full access is not just read-only permission; it allows changing and deleting items. If the work requires that deletion is not allowed, separately determine whether the shared mailbox meets the requirement.
Changing the responsible person and reverting incorrect permissions
After the new responsible person completes the read/send test, remove the existing person from full access and each send permission list. Do not delete just one permission and treat it as if all access has been revoked. Check that the permission changes were saved and test access in a new session, and preserve the mailbox itself and past emails according to the handover plan. When permissions are added incorrectly, only revoke the specific items and do not delete the mailbox to reverse it.
