Send Power Automate emails from a shared mailbox

Use the Office 365 Outlook action "Send an email from a shared mailbox (V2)" and enter the shared mailbox address in Original Mailbox Address. The account behind the connection needs permission on that mailbox, which an admin gives.

A Power Automate email is normally sent by the account that made the connection, so it looks like it came from a person. When that person leaves, or is out, replies go to a mailbox nobody else reads. Sending from the team address fixes that. An admin gives the permission, so ask your admin.

Menu and action names in Microsoft 365 change from time to time. The exact names may differ on your screen. The Microsoft pages behind each step are listed at the end.

Why the sender matters

Think of a flow that emails customers when a request is received, or emails the team when a task is late. If the message comes from one person, three things go wrong:

Customers reply to that person, not to the team.
When that person is out or leaves, the replies sit unread.
The team cannot see what was sent, because the copy is in one person's sent items.

A shared mailbox fixes all three. Microsoft describes a shared mailbox as a way for a group to monitor and send email from a common address. Recipients see the shared address in the message.

Two actions that look alike

The Office 365 Outlook connector lists these actions. The descriptions below come from Microsoft's connector page.

Send an email (V2): "This operation sends an email message." This sends from the account in the connection.
Send an email from a shared mailbox (V2): "This operation sends an email from a shared mailbox. Your account should have permission to access the mailbox for this operation to succeed."

The older action named "Send an email from a shared mailbox" is deprecated. Microsoft's page says: "This action has been deprecated." If your flow still uses it, switch to the V2 action.

Microsoft's page lists these limits for the V2 action: "The operation is expected to work for the Microsoft 365 shared mailbox feature only." and "Action does not work for shared mailboxes that were converted from personal mailboxes." It also says "An Office 365 group address can't be used as shared mailbox address."

Use the V2 action when the sender must be the team address. If your screen shows slightly different names, look for the word "shared mailbox" in the action name.

The Microsoft connector page also lists an optional "Original Mailbox Address" field on other actions, such as Get emails and Forward an email. It is described as the address of the shared mailbox. Microsoft's pages do not describe a single setting that turns every action into a shared mailbox action, so choose the action that names the shared mailbox.

The permission you need

The account in your flow connection needs permission on the shared mailbox. Microsoft's Exchange Online page describes three permissions:

Full Access: the person can open the mailbox and see its content. It does not allow sending messages from the mailbox.
Send as: messages appear to come directly from the mailbox. Microsoft says there is no indication that a delegate sent the message.
Send on behalf: the From address shows the sender "on behalf of" the mailbox. Microsoft says replies to these messages go to the mailbox, not to the delegate.

Microsoft also says that if a person has both Send as and Send on behalf, Send as is used.

Microsoft's pages do not describe which of these two the shared mailbox action requires, only that the account "should have permission to access the mailbox". One way to start: ask your admin for Send as for the flow account, run the test below, and look at how the message appears. If your team prefers that the person behind the flow is shown, ask for Send on behalf instead.

Do not try to set this up yourself in a way that gives out more access than the flow needs. Permissions on mailboxes are an admin task. Say "ask your admin", and send them the name of the shared mailbox and the account your flow uses.

Checklist before you build

Name the shared mailbox and its address.
Name the account the flow will use. A shared account that more than one person can manage is safer than one person's account.
Ask your admin to give that account permission to send from the shared mailbox.
Plan for a wait after the admin grants permission. Microsoft says: "After the permissions are granted for the account to access the shared mailbox, it can take about two hours until the permissions are replicated on the platform." Test after the admin confirms.
Name two owners for the flow, so it does not stop when one person leaves. See the siblings below.
Write down who reads the shared mailbox, and how often.

Step 1. Add the action

Open your flow in Power Automate. Choose the step where the email should go.
Choose Add an action and search for "shared mailbox".
Under Office 365 Outlook, choose "Send an email from a shared mailbox (V2)".
Sign in with the flow account if asked. This is the connection that needs the permission above.

Step 2. Fill in the fields

Microsoft's connector page lists these fields for the action.

Original Mailbox Address: required. The address of the shared mailbox, for example the team address.
To: required. One or more addresses separated by semicolons.
Subject: required.
Body: required.
CC and BCC: optional.
Reply To: optional. The addresses to use when replying.
Sensitivity and Importance: optional.

The attachment fields on that page, Name and Content, are only needed when you attach a file.

Keep the subject plain and specific, for example "Your request was received". Put the list item Title in the body, so the reader can tell which request it is about.

Step 3. Decide where replies go

Replies are what make shared mailboxes useful, so decide this on purpose.

If the message is sent from the shared mailbox, a reply normally goes to the sender address. For Send as, that is the shared mailbox.
If you use Send on behalf, Microsoft says replies go to the mailbox, not to the delegate.
The Reply To field lets you set a different reply address. Use it only when replies should go somewhere other than the sender.

Then make sure someone owns the shared inbox. If replies arrive and nobody tracks them, the problem moves from one inbox to another. See "Requests lost in a shared inbox: add an owner and a status".

Step 4. Test with one email

Do not turn the flow on for everyone first.

Put your own address in the To field.
Run the flow once with one real example.
Open the run history and check the action shows as succeeded.
Open the email. Read the From line. Does it show the shared address, or a person "on behalf of" the shared address?
Reply to the email. Check the reply lands in the shared inbox.
Write down the date and the result in your flow list.
Change To to the real recipients and run one more test with a colleague.

If the action fails, read the error in the run history. A permission message usually means the admin step is not finished, or the flow is using a different account than the one that got permission. Send the exact error text to your admin.

Which error means what

Our advice, not a Microsoft rule, unless a line names Microsoft.

Permission denied: the flow account lacks permission on the mailbox, or the permission was granted under two hours ago. Microsoft gives the two hour replication note above. Check with your admin.
Mailbox not found: check the address in Original Mailbox Address for typos. Then check that it is a Microsoft 365 shared mailbox, not a group address, and not one converted from a personal mailbox. Both limits come from Microsoft's page above.
Works for you, fails for a colleague: the connection belongs to one account. Check which account the flow connection uses.

What to avoid

Auto-reply loops. If the shared mailbox has an auto-reply, and your flow starts when mail arrives in that mailbox, the flow can answer the auto-reply, which answers again. Do not build a flow that replies to every message in the same mailbox it sends from. Add a condition that skips messages from your own address and from automatic senders.
Sending too many. One email per event is the rule. A flow that loops over a list and sends one message per row can flood a shared mailbox and the people who read it. Combine the rows into one message. Microsoft publishes limits for connectors and flows, so check the pages linked in the sources and with your admin.
Using one person's sign-in for the flow. When that person leaves, the flow fails. Ask your admin for an approved account.
Skipping the test. A flow can show On and still fail on every run. Read the first run.
Sending from an address you have no permission on. The action will fail, or your admin may notice.
Putting private details in subjects. Keep subjects short and general.

For late-task emails, see "Late tasks nobody notices: setting up late alerts". For emails that go out before a due date, see "Send a reminder before a due date in a SharePoint list".

Honest limits

This guide covers the Office 365 Outlook connector in Power Automate cloud flows. Action names, fields and permission screens can change, and your tenant may have settings that differ. Mailbox permissions are an admin task. Licensing for connectors differs by plan, so check with your admin. Microsoft's pages do not describe which mailbox permission the action needs, so test it before you rely on it.

When to get help

You can build all of this yourself in Microsoft 365. If you would rather have it built and tested for your team, I do that. A tracker like this is a fixed price: $5,000 for one, built in 2 weeks. See "What a SharePoint tracker costs to build". Bring one example of the problem to a free call.

Tell me what's still manual

I am Al Davies. I run 250 High Street LLC and build SharePoint trackers and Power Automate flows for operations teams. I work remotely. The first call is free, and I will not try to sell you anything.

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FAQ

Why does send from a shared mailbox not work?

Check four things: the V2 action is used, the mailbox is a Microsoft 365 shared mailbox not converted from a personal one, the flow account has permission, and about two hours have passed since the permission was granted, as Microsoft's page says.

How do I send from a shared mailbox with an attachment?

Microsoft's connector page lists attachment Name and Content fields on its email actions, and a maximum mail content length of 49 MB. Test with one small file first.

How do I forward an email from a shared mailbox?

Use the "Forward an email (V2)" action and fill the Original Mailbox Address field with the shared mailbox address, which Microsoft describes as the "Address of the shared mailbox to forward mail from."

Can I send from a group mailbox?

Microsoft says "An Office 365 group address can't be used as shared mailbox address." Use a Microsoft 365 shared mailbox.

What is the difference between Send as and Send on behalf?

Microsoft says Send as makes the message appear to come directly from the mailbox, while Send on behalf shows the delegate "on behalf of" the mailbox. Ask your admin which fits your team.