Outlook: Send on Behalf of a Shared Mailbox

Yes. You can send an Outlook message on behalf of a shared mailbox if an Exchange administrator has granted your account the mailbox’s Send on Behalf permission. Once it is in place, choose the shared mailbox in the message’s From field; recipients will be able to see both the mailbox and the person who sent the message.

What “send on behalf” means

A shared mailbox is an Exchange mailbox that multiple authorized people can use, often for an address such as support@company.com or invoices@company.com. It lets a team handle incoming messages from a common address without sharing one person’s password. Outlook may show the mailbox alongside your own, but seeing or reading it is a separate matter from having permission to send from it.

With Send on Behalf permission, a recipient generally sees a sender description such as “Jordan Lee on behalf of Support.” The message identifies the shared mailbox as the address represented, while also revealing which delegate sent it. This can be useful when a team wants a consistent public-facing address but needs recipients to know who handled a particular message.

The permission is assigned in Exchange, not created merely by typing the shared address into Outlook. If you do not have the required permission, Outlook may let you compose a message with that address in From, but sending can fail with an access or permission error.

Send on Behalf, Send As, and mailbox access

These permissions solve different problems, so it helps to confirm which one your organization intends to use. Send on Behalf identifies both the delegate and the shared mailbox to recipients. Send As makes the message appear to come from the shared mailbox alone; recipients generally do not see the delegate’s name in the sender display. Neither sending permission automatically means you can open and read the mailbox.

Full Access lets an authorized user open and work with mailbox contents. By itself, it does not grant permission to send as or on behalf of the mailbox.
Send on Behalf authorizes sending with the delegate identified as acting for the mailbox.
Send As authorizes sending so the message appears to come directly from the mailbox.

An administrator can grant Full Access and a sending permission together, or grant only the permissions the role requires. For example, a person who drafts replies from a shared inbox will commonly need access to its messages as well as Send on Behalf or Send As. A person who sends occasional announcements from the team address might need sending permission without needing to read the mailbox.

How an administrator grants permission

Send on Behalf permission must be granted by someone with appropriate Exchange or Microsoft 365 administrative rights. In the Exchange admin center, an administrator can select the shared mailbox and add the relevant users under its mailbox delegation or sending permissions. The exact labels and navigation can change as Microsoft updates the admin center, but the permission to look for is specifically Send on behalf.

Exchange administrators can also manage the permission with Exchange Online PowerShell. For example, a command in this form adds a delegate while retaining existing entries:

Set-Mailbox -Identity support@company.com -GrantSendOnBehalfTo @{Add="jordan@company.com"}

Administrators should check the mailbox identity and delegate address carefully before running a command, and follow their organization’s change-control process. A user who cannot administer Exchange should ask the help desk or mailbox owner to request the permission rather than trying to work around the restriction by changing the From address.

Permission changes can take time to become effective across Microsoft 365 and Outlook. If an administrator has just added you, wait a while, restart Outlook or refresh Outlook on the web, and test again. If the mailbox has been shared with a group rather than directly with you, the administrator should verify that the group-based arrangement supports the permission and access pattern the organization expects.

Choose the shared mailbox in Outlook

After permission is granted, create a new message and display the From field if it is not already visible. In classic Outlook for Windows, the From control is available from the message window, often on the Options tab. In new Outlook and Outlook on the web, use the message’s options or From control to show or select the sender address. Microsoft changes interface labels periodically, so the important step is to expose the From field rather than rely on one exact menu path.

Start a new email message.
Show the From field if it is hidden.
Open the From list and select the shared mailbox. If it is not listed, choose the option to enter another email address and type the mailbox’s address.
Check that the displayed address is the intended shared mailbox, then write and send the message.

Outlook may remember an address after you have used it. That convenience can also preserve a stale or incorrect suggestion, so verify the full address when the message is important. If the mailbox does not appear automatically, that does not by itself prove the sending permission is missing: the From list, mailbox visibility, address book, and permission are related but separate parts of the experience.

Where the sent message is saved

A frequent surprise is that a message sent on behalf of a shared mailbox may appear in the delegate’s personal Sent Items folder rather than in the shared mailbox’s Sent Items. Sending permission determines whether you may send; it does not necessarily determine where Outlook stores the sent copy. This can make it harder for coworkers to see what the team has already answered.

An Exchange administrator can configure the shared mailbox to keep copies of messages sent on behalf of it. In Exchange Online, the mailbox setting commonly used for this purpose is MessageCopyForSendOnBehalfEnabled. The administrator can check the current configuration and change it according to the team’s recordkeeping needs. Do not assume that a message is missing simply because it is not in the shared folder; check the sender’s Sent Items and ask the administrator how the mailbox is configured.

For a team that needs a shared history, agree on a consistent process. That might include configuring shared Sent Items copies, using a supported shared-mailbox workflow, or documenting which folder staff should check. Avoid moving or deleting sent messages as a substitute for a clear retention policy, particularly when the mailbox is used for customer service, finance, or regulated work.

Common problems and practical checks

If Outlook reports that you are not allowed to send, first confirm that the administrator granted Send on Behalf to the account you are actually using. Full Access alone is not enough. Also confirm that you selected the correct mailbox in From; selecting a similarly named address or an old autocomplete entry can cause confusing results.

Permission was just added: Allow time for the change to take effect, then restart Outlook or sign out and back in to Outlook on the web.
The mailbox is missing from the folder list: Ask whether you have Full Access. Send permission and the ability to open the mailbox are distinct. You may still be able to send if you have sending permission and can enter the address, but you will not necessarily see its inbox.
The From field is hidden: Show it in the compose window before trying to select the shared address.
Outlook keeps choosing the wrong address: Remove or avoid the stale autocomplete suggestion, then enter the verified mailbox address again.
The message sends but recipients see the wrong identity: Confirm whether you were given Send on Behalf or Send As, and check the actual From address before sending another message.
Colleagues cannot find the sent copy: Check both the delegate’s Sent Items and the shared mailbox’s Sent Items, then ask an administrator about copy settings.

If the issue continues, provide the help desk with the exact error, the Outlook version or web client you used, the mailbox address, and the approximate time of the test. That information helps distinguish a permission problem from an Outlook display issue or a mail-flow restriction. Do not forward passwords or ask a coworker to sign in as the shared mailbox; shared mailboxes are generally intended to be accessed through each user’s own authorized account.

Privacy, identity, and organizational policy

Send on Behalf is transparent about who sent the message, which can improve accountability. It is not a way to impersonate the mailbox owner without disclosure. If a department expects the shared address to appear as the sole sender, ask an administrator whether Send As is appropriate and permitted by policy. A different sender display does not remove the organization’s ability to retain or audit messages under its Microsoft 365 configuration.

Keep access limited to people who need it, and have an administrator remove permissions when someone changes roles or leaves the team. A shared mailbox is not normally meant to be accessed by signing in directly with a shared password. Use individual accounts and assigned permissions so that access can be managed and actions can be attributed to the right person.

Licensing and storage requirements depend on the mailbox’s size, features, and the organization’s Microsoft 365 plan. Many standard shared-mailbox scenarios do not require a separate license for the mailbox itself, but the people accessing it generally need their own eligible accounts, and additional capacity or features can have licensing requirements. Ask your Microsoft 365 administrator to check the organization’s current license terms rather than assuming every shared mailbox is free of restrictions.

Frequently Asked Questions

Can I send on behalf of a shared mailbox without Full Access?
Potentially, yes. Send on Behalf and Full Access are separate permissions. You need Send on Behalf to send in that capacity, while Full Access is what allows you to open and work with the mailbox contents.

Why can I open the shared mailbox but not send from it?
You may have Full Access without a sending permission. Ask an Exchange administrator to check whether you need Send on Behalf or Send As and grant the intended permission.

Will recipients know who sent a message on behalf of the mailbox?
Generally, yes. The sender display identifies the delegate acting on behalf of the shared mailbox. With Send As, recipients generally see the shared mailbox as the sender instead.

Why does Outlook show the shared mailbox in From but reject the message?
The From field can accept an address even when your account lacks authorization. Verify that the correct sending permission has been granted and has had time to take effect, then try again.

Do messages sent on behalf of a shared mailbox appear in its Sent Items?
Not necessarily. They may be saved in the sender’s Sent Items unless an administrator has configured copies to be kept in the shared mailbox. Check both locations or ask the administrator about the mailbox setting.

When to use another approach

Send on Behalf is a good fit when the shared address represents a team but recipients should also know which person replied. Choose Send As when your organization wants the shared mailbox to appear as the sender without the delegate name, subject to policy. If several people need to manage a high volume of messages, consider whether a shared mailbox is still the right workflow or whether an approved customer-service or ticketing system would provide better assignment, tracking, and reporting.

In every case, the reliable sequence is the same: decide how the sender should appear, have an administrator grant the matching Exchange permission, expose and verify the From address in Outlook, and confirm where sent copies are stored. That prevents the most common confusion: assuming that seeing a shared mailbox, opening it, and sending from it are all controlled by one permission.

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