How to Send Email From a Shared Mailbox in Outlook

Sending from a shared mailbox address sounds simple until you open a new message and realize there is no way to change the From line. The From field is hidden by default in both classic and new Outlook, and even when you find it, it will only show the shared address if your admin has granted you the correct permission.

Get either of those things wrong and the message goes out from your personal address instead of the team account, or it arrives at the recipient showing '[Your name] on behalf of [shared mailbox]' when your policy says it should not. This guide covers every step on all four Outlook surfaces — classic Outlook, new Outlook for Windows, the web app, and mobile — together with the two permission types that determine what recipients see.

By the end you will know which setting to check when the From field is missing, exactly why the 'on behalf of' text appears, and how to make the shared address the automatic default for replies inside that mailbox.

The short answer#

In classic Outlook: open a new message, go to the Options tab, click From, then select the shared mailbox address from the dropdown. In new Outlook and the web app: open a new message, click your name in the From line, and choose the shared address. On mobile the process varies by app version and is more limited.

If the shared address does not appear in the dropdown, your admin has not yet granted the necessary permission. That is the most common reason the From option either omits the shared address entirely or does not appear at all.

Before you start: two permission types#

Before you touch the From field, confirm which permission your admin has assigned. The permission type controls what recipients see and determines which address appears in the dropdown. There are two options, and they are not interchangeable.

Send As makes the message appear to come directly from the shared mailbox. The recipient sees only the shared address in the From line, with no indication of who on the team sent it. This is the right permission for a team address like [email protected] where all replies should look identical regardless of who sends them.

Send on Behalf of makes the message show '[Your display name] on behalf of [shared mailbox]' in the From line. Technically the message still comes from the shared mailbox, but recipients can see who composed it. Some organizations prefer this for accountability; others find it looks inconsistent for a shared support or billing address.

Both permissions are set by an admin in the Microsoft 365 admin center or Exchange admin center — you cannot grant them yourself. If you are unsure which one you have, send a test to a personal address and check how it appears on arrival.

How to send from a shared mailbox in classic Outlook#

These steps apply to Outlook for Microsoft 365 (subscription) and Outlook 2019 and 2021 on Windows and Mac. The steps are the same whether you opened the shared mailbox as an additional account or as a delegated folder inside your own account pane.

1. 1

   Show the From field

   Open a new message or open a reply. Go to the Options tab in the ribbon and click the From button. The From field now appears at the top of the compose window, above the To line. You only need to do this once — Outlook remembers the setting for future messages in the same profile.

2. 2

   Select the shared mailbox address

   Click inside the From field. A dropdown appears listing addresses associated with accounts you have permission to send from. Select the shared mailbox address. If the address is not listed, stop here — your admin has not granted Send As or Send on Behalf of permission yet, or the permission has not yet replicated (see troubleshooting below).

3. 3

   Compose and send

   Write your message normally and send. If you have Send As permission the recipient sees only the shared address. If you have Send on Behalf of permission they see '[Your name] on behalf of [shared mailbox]'. Replies from recipients go to the shared mailbox inbox, not your personal address.

4. 4

   Make it the default for replies in that mailbox

   To reply from the shared address automatically when reading mail in the shared mailbox folder, add the shared mailbox as a separate account in Outlook: File > Add Account, enter the shared mailbox address, and authenticate. Once added as a full account, when you reply from within that account's folder Outlook pre-fills the From field with the shared address rather than your primary account.

How to send from a shared mailbox in new Outlook and the web#

New Outlook for Windows and Outlook on the web (outlook.office.com) share the same interface architecture, so the steps below apply to both. The From field works differently here than in classic Outlook — it is visible in the compose window by default, but only populates with addresses for mailboxes you have Send As or Send on Behalf of access to.

1. 1

   Open a new message or reply

   Click New Message, or open an existing thread and hit Reply. The compose pane opens on the right side of the screen.

2. 2

   Click on the From address

   In the compose window, click directly on your name or email address in the From line. A dropdown appears showing any shared mailboxes or additional addresses you have access to. Select the shared mailbox address.

3. 3

   If no dropdown appears

   If clicking From does nothing or shows only your own address, you have either not been granted Send As or Send on Behalf of permission, or the shared mailbox has not been added to your account. Confirm with your admin. You cannot change the From address without one of those two permissions in place.

4. 4

   Set replies to default to the shared address

   New Outlook does not support setting a per-folder default From address the same way classic Outlook does. If the shared mailbox is added as a separate account in new Outlook, replies from within that account's folder should default to the shared address automatically. If they do not, check with your admin whether the mailbox is configured as a full account or only as a delegated view.

Platform differences at a glance#

The core permission requirement is the same across all surfaces — Send As or Send on Behalf of must be granted by an admin — but where to find the From field and how much automatic defaulting is available varies by platform.

What to do when it does not work#

The most common problems when sending from a shared mailbox fall into four categories. Work through them in order — each one rules out the next.

The From option is missing or shows only your personal address. This means you have not been granted Send As or Send on Behalf of permission, or the permission has not yet replicated across Microsoft's servers. Permissions in Microsoft 365 can take up to 60 minutes to propagate after an admin saves the change. If it has been less than an hour, wait, close and reopen Outlook, and try again. If it has been longer, ask your admin to confirm the grant in the Microsoft 365 admin center: Users > Active users > select your account > Mail tab.

The message arrives showing 'on behalf of' when you expected only the shared address. You have Send on Behalf of permission rather than Send As. Both permissions are legitimate, but they produce different From headers. Ask your admin to change the grant to Send As if the policy requires the pure shared address with no sender attribution.

You get a send permission error or the message bounces back. Your admin likely granted Full Access — which lets you open and read the mailbox — but did not separately add Send As or Send on Behalf of. These are distinct grants; Full Access alone does not authorize sending from that address. Both can be set together, but they must each be set explicitly.

Replies from within the shared mailbox folder still default to your personal address. The shared mailbox needs to be added as a separate full account in Outlook, not only as a delegated folder. When you reply from within a full account's folder, Outlook uses that account's From address automatically. If it was added only as a delegated folder in your existing account, Outlook defaults to your primary account's address and you must change the From field manually each time.

A faster way to handle shared mailbox email#

Configuring the From field and managing shared mailbox replies manually works, but for a team handling volume across multiple shared addresses it is the kind of setup that breaks every time someone changes roles, an admin resets a permission, or a new team member joins and has to repeat the process from scratch.

AI Emaily connects shared mailboxes alongside every personal account in one unified inbox. It routes each reply to the correct From address automatically based on which mailbox the thread arrived in, drafts replies in the account's voice using user-set Context and per-client profiles, and keeps an audit trail of every send. The approval-before-send Copilot mode means nothing leaves the shared address without a human confirming it first. We build AI Emaily — see how it handles shared inboxes at aiemaily.com/pricing, and try it free for seven days.