Sending from a shared mailbox in Outlook comes down to one control: the From field. Once your admin has given you Send As or Send on Behalf permission, you choose the shared address there and the message goes out under it. The part that trips teams up comes after you click Send, when the reply files itself into your personal Sent Items instead of the shared mailbox's.
Open a new message and show the From field: Options > Show From in new Outlook, Options > From in classic, More actions > Show From on the web. Select the shared address and send. You need Send As or Send on Behalf; Full Access alone cannot send. To keep copies in the shared mailbox's Sent Items, an admin turns on the Sent items setting, or sets MessageCopyForSentAsEnabled and MessageCopyForSendOnBehalfEnabled to $true.
How do you send email from a shared mailbox in Outlook?
The From field is hidden by default in every Outlook client, because a single-account user never needs it. Once you reveal it, it stays visible and lists every address you are allowed to send from.
The steps below were verified October 2026 against Microsoft's Open and use a shared mailbox in Outlook and Add a shared mailbox to Outlook on the web. If the mailbox is not in your Outlook yet, start with how to add a shared mailbox in Outlook.
New Outlook for Windows
- Select Mail, then Home > New > Mail.
- If there is no From field above the To line, select Options > Show From.
- Select From, then pick the shared mailbox address. If it is not listed, choose Other email address and type it.
- Write and send. When replying to a message in the shared Inbox, check the From field first; the dropdown fixes it if your own address is selected.
Classic Outlook for Windows
- Choose New Email.
- If From is hidden, choose Options > From on the ribbon.
- Select From, pick the shared address, or choose Other email address, type it and select OK.
- Select Send. For replies, use the From dropdown on the open message if the shared mailbox is not already selected.
Outlook on the web
- Choose New mail, then select the More actions menu at the top of the message and choose Show From.
- The first time, right-click the From address, choose Remove, and type the shared mailbox address. After that it sits in the From dropdown.
- Add recipients, write and select Send. For a reply, select Reply, then More actions > Show From, and swap the address the same way.
Outlook for Mac and Outlook mobile
Outlook for Mac supports Full Access only on shared mailboxes, and Microsoft's Mac article stops at opening the mailbox. Ask your admin for Send As on top of Full Access. Add the mailbox under Tools > Accounts as described in the guide above, then choose the shared address in the From menu of a new message.
On iPhone and Android, the shared mailbox sits in your account list after you add it. A message started from that mailbox goes out from its address.
Send As vs Send on Behalf, and why Full Access is not enough
Microsoft 365 separates opening a mailbox from sending as it. Three permissions exist, documented on Create a shared mailbox.
- Full Access lets you open the mailbox and act as its owner: read, delete, file, create calendar items. It does not let you send from the address.
- Send As makes the message appear to come from the shared mailbox itself. The recipient sees 'Contoso Support' and nothing else.
- Send on Behalf shows both names. The recipient sees 'Priya Nair on behalf of Contoso Support'.
A support or sales address wants Send As, because the customer should see one identity. Send on Behalf suits an assistant sending for an executive, or a compliance setting where the author must stay visible.
Admins grant Full Access and Send As in the Microsoft 365 admin center under Teams & groups > Shared mailboxes > Manage mailbox permissions. The Exchange admin center has the same under Recipients > Mailboxes > Manage mailbox delegation. Send on Behalf is set with Set-Mailbox and the GrantSendOnBehalfTo parameter.
Two gotchas. Right after a permission change, you may see an error that you do not have permission to send on behalf of the specified user. That is replication latency, and Microsoft says it clears in about an hour. The second: if the shared mailbox is hidden from the global address list, Send As and Send on Behalf stop working in the Outlook desktop client. Both need the mailbox visible there.
Why sent items land in your personal Sent Items folder
By default, a message you send as the shared mailbox is saved to your own Sent Items, and the shared mailbox's Sent Items stays empty. Microsoft's explanation is mechanical. You never sign in to a shared mailbox; you sign in to your own and open the shared one. Outlook therefore sends from your account and files the copy there.
The troubleshooting article is Messages sent from a shared mailbox aren't saved to the Sent Items folder, verified October 2026. For a team this is the single most damaging default. The customer's thread shows the question in the shared Inbox and nothing after it. Reconstructing what was said means asking each teammate to search their own Sent folder. The fix is an admin setting on the mailbox, and it takes a minute.
The admin fix: copy sent messages to the shared mailbox
In the Microsoft 365 admin center, go to Teams & groups > Shared mailboxes, select the mailbox, and select Edit under Sent items. Turn on the options for items sent as and sent on behalf of the mailbox, then save. Microsoft's Configure shared mailbox settings page describes this as allowing everyone to see the Sent email.
The same two switches in Exchange Online PowerShell, after Connect-ExchangeOnline:
- Set-Mailbox support@yourcompany.com -MessageCopyForSentAsEnabled $true
- Set-Mailbox support@yourcompany.com -MessageCopyForSendOnBehalfEnabled $true
Both parameters default to $false, per the Set-Mailbox reference. Once on, a copy is written to the shared mailbox's Sent Items and your own copy stays in yours, so nothing is lost. Microsoft notes that new Outlook supports only this server-side method.
Classic Outlook in cached mode also has an older client-side registry value, DelegateSentItemsStyle, which moves the copy instead of duplicating it. The server setting is the one to use, since it works in every client and needs no per-PC change.
| MessageCopyForSentAsEnabled | DelegateSentItemsStyle (classic Outlook) | Result |
|---|---|---|
| $false (default) | 0 (default) | Copy in your Sent Items only |
| $true | 0 | Copy in your Sent Items and in the shared mailbox |
| $false | 1 | Copy in the shared mailbox only |
| $true | 1 | Two copies in the shared mailbox, none in yours |
What the shared Sent Items still cannot tell you
With the copy setting on, the shared mailbox holds the whole conversation, inbound and outbound, in one place. It is a per-mailbox setting an admin has to know about, and once on it records the mail and nothing more.
The folder does not say which teammate sent each reply as 'Contoso Support'. It does not show whether anyone has picked up the newest message, or what was promised in the reply from six weeks ago. Those are the questions a team starts asking once more than two or three people share the address.
We build Sektra, a separate shared inbox workspace that syncs two-way with Microsoft 365, shared mailboxes included. Replies sent from Sektra go out through the shared mailbox and show up in Outlook like any other. Each one carries the teammate who sent it, the owner of the thread, and any internal notes.
The memory layer is the record Sektra builds per contact of commitments made and questions left open. It reads the Sent Items history too, so what was promised is a question the assistant can answer. Outlook connects through Microsoft sign-in, and Sektra never sees that password.
See the Outlook integration page, the connect an Outlook shared mailbox help article, and where an Outlook shared mailbox stops. Account management teams sending from a shared client address have their own page at Sektra for account management.
Turn the Sent items switch on today regardless. It costs nothing, and it makes the shared mailbox a complete record of what the team said.
