Exchange mailbox permissions are separate capabilities, not one all-purpose access switch. Full Access lets a delegate open and manage mailbox contents; Send As lets them send as the mailbox; and Send on Behalf lets them send with their delegate role visible. A shared mailbox commonly needs Full Access plus a separate sending permission.
What is the difference between Full Access and Send As?
The practical difference is access to mailbox contents versus authority over the sender identity. Microsoft documents these as distinct permissions in Exchange Online and Exchange Server.
| Permission | Read or manage mailbox contents? | Send from the mailbox? | What recipients see |
|---|---|---|---|
| Full Access | Yes. The delegate can open the mailbox and view, add, and remove content. | No, not by itself. | No sender presentation is granted by this permission. |
| Send As | No. It does not grant mailbox-reading access. | Yes. | The message appears to come from the mailbox or group, without indicating in the From presentation that the delegate sent it. |
| Send on Behalf | No. It does not grant mailbox-reading access. | Yes. | The From presentation identifies the delegate as sending on behalf of the mailbox or group. |
If a delegate has both Send As and Send on Behalf, Microsoft says Send As is used. Choose the permission that matches the recipient-facing identity you intend.
How do I give someone access to a shared mailbox?
For a delegate who needs to open and manage a shared mailbox and send messages from it, grant two distinct permissions: Full Access for mailbox contents, then either Send As or Send on Behalf for sending. If the delegate only needs to read or manage the mailbox, Full Access may be sufficient. Assigning delegate permissions is not the same as giving someone the mailbox’s sign-in credentials.
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Exchange Online
Use the Exchange admin center or Exchange Online PowerShell to assign supported permissions for the recipient type. The available workflow differs by permission: Microsoft notes that the general Exchange admin center permissions workflow does not provide shared-mailbox Send on Behalf. Its shared mailbox guidance describes using the Set-Mailbox cmdlet for that permission. Check the current instructions for the mailbox type and interface you are administering rather than assuming one path covers every grant.
Exchange Server
Exchange Server has its own recipient permissions guidance and administrative workflows. Follow the Exchange Server documentation for the server version and recipient involved; do not assume Exchange Online interface labels or procedures apply unchanged.
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Pick the sending permission by the intended From presentation
- Choose Send As when the message should appear to come from the shared mailbox itself.
- Choose Send on Behalf when recipients should be able to see which delegate sent the message on the mailbox’s behalf.
- Do not add a sending permission if the delegate only needs to open or manage mailbox contents.
Can Full Access send email from a mailbox?
No. Full Access permits opening and managing mailbox contents; it does not grant Send As or Send on Behalf. Add one of those separately if the delegate needs to send from that mailbox. This separation lets an administrator grant content access without automatically authorizing outbound messages under the mailbox identity.
Why did a shared mailbox appear automatically in Outlook?
In Exchange Online, Full Access granted directly to an individual can cause the mailbox to appear in that delegate’s Outlook profile through Autodiscover. This auto-mapping behavior does not apply to each member when Full Access is assigned through a group. Microsoft’s Add-MailboxPermission reference documents the -AutoMapping $false option for granting Full Access to an individual without auto-mapping the mailbox.
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Auto-mapping is an Outlook convenience, not an additional permission. The delegate’s actual mailbox access comes from Full Access.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What should administrators check before granting delegation?
Limit access to the required scope
Full Access applies to the mailbox, not just one folder. If a person needs access only to a particular folder, consider folder-level permissions instead of granting mailbox-wide access. Folder permissions alone do not grant Send As or Send on Behalf; Microsoft’s EWS delegate guidance makes that distinction explicit.
Consider private items
Full Access can expose content marked Private. Microsoft’s Exchange Server permissions guidance warns that delegates with Full Access can access mailbox content including private items; the Add-MailboxPermission reference also describes access to all items, including calendar items marked Private, in Exchange Online and modern Outlook experiences. Confirm current behavior for the environment and client in use before relying on a privacy distinction.
Account for hybrid configuration
In hybrid deployments, mailbox location and where permissions are configured can affect the setup. Microsoft’s hybrid permissions guidance discusses cross-environment Send on Behalf scenarios, manual Send As configuration in both environments for many scenarios, and auto-mapping. These details are not a single recipe for every hybrid topology; follow the guidance for the specific deployment.
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Confirm recipient type and permission scope
Exchange Online permission support and workflow can vary by whether the target is an individual mailbox, shared mailbox, or group. Before applying a procedure, confirm the Exchange environment, recipient type, whether access should cover the whole mailbox or one folder, and whether sending is required.
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