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How to send a mail merge from a shared mailbox in Power Automate
Send a personal email to every client on an Excel list from a shared mailbox like support or sales. Replies come back to the shared inbox, and the whole team can see what was sent.
Jump to a step (9)
This is for small offices that send mail merges with Power Automate. The standard flow sends every email from your own address, so clients reply to you personally, replies get lost when you are away, and nobody else can see what was sent. Sending through a shared mailbox fixes this.
I start from a standard mail merge flow: Manually trigger a flow, List rows present in a table reading the Clients table, and an Apply to each loop with two Compose actions called Subject text and Body text. There is no send action in the loop yet. If you need to build that flow first, there is a separate video on the Technologiate channel. All the text and expressions from the video are free to download on this page.
What you need
- A Microsoft 365 work or school account with Power Automate, Excel for the web and Outlook. Your own user needs a licensed Exchange Online mailbox.
- No premium connectors. The flow only uses Excel Online (Business), Office 365 Outlook and Power Automate.
- A shared mailbox, for example a support mailbox. A basic shared mailbox needs no license of its own up to 50 GB.
- The Send As permission on the shared mailbox for the account the flow's Outlook connection uses. An admin sets this in the Exchange admin center. Being a Microsoft 365 admin does not give you this permission automatically.
- An Excel table named Clients with the columns Client, Contact name, Email and Visit day.
- A mail merge flow with Subject text and Body text Compose actions inside Apply to each.
Step by step
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01
Check the shared mailbox permissions
Open the Exchange admin center, go to the mailboxes and click your shared mailbox. Click Delegation. Click Edit under Read and manage and under Send as, and check that your account is on both lists. Send on behalf is a different permission that this guide does not use, so that list can stay empty.
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02
Add the shared mailbox action
In Power Automate, open the flow in edit mode and click the plus icon below Body text inside Apply to each. In the search box, type
send an email from a sharedand select Send an email from a shared mailbox (V2) from Office 365 Outlook. At the bottom, check the account the action is connected to. The action runs as this account, so the permissions from step 1 must belong to it. -
03
Enter the shared mailbox address
In Original Mailbox Address, type your shared mailbox's address. Select the mailbox's entry from the list, not the Use ... option above it.
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04
Fill in To, Subject and Body
- To: click the gear icon next to To, select Use dynamic content, click the To field, click the lightning icon, search for email and select Email
- Subject: click the field, click the lightning icon and select Outputs under Subject text
- Body: click the field, click the lightning icon and select Outputs under Body text
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05
Rename the action and save
Rename the action to Send from Support mailbox and press Tab. Click Save.
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06
Test the flow
Click Test, select Manually and click Test. If the connections screen shows, click Continue. Click Run flow, then Done. Every step should complete, and Apply to each shows the send action ran once for each client.
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07
Check the email and reply to it
In a client's mailbox, open the holiday schedule email. The From line shows only the shared mailbox, with no "on behalf of", and the body starts with the contact's name. Click Reply: the reply goes to the shared mailbox.
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08
Check the shared inbox and Sent Items
Open the shared mailbox's inbox. The client's reply is there, and nothing came to your own inbox. Click Sent Items: the emails from the flow are in the shared mailbox's Sent Items, not in yours.
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09
Fix the Send As permission error
If the run fails with
You are not authorized to send mail on behalf of the specified sending account., click the Send from Support mailbox action. A status of Forbidden (403) and the error codeErrorSendAsDeniedmean the connection account has Full Access but no Send As. Ask an admin to add that account under Send as in the Exchange admin center. Then wait and test again.
Tips and common problems
- New permissions can take an hour or two to apply, so if your first test fails, wait and try again. In my test it worked after 19 minutes.
- Full Access (Read and manage) lets you open and read the mailbox, but not send from it. You need Send As as well.
- The permissions must belong to the account of the action's connection, which does not have to be the flow's owner.
- Microsoft says this action does not work with a shared mailbox that was converted from a personal mailbox.
- When you enter the mailbox address, select the mailbox entry from the list, not the Use ... option.
- In my test the admin setting called copy items sent as this mailbox was off, and the copies still landed in the shared mailbox's Sent Items.
Questions
Do I need a premium license for this?
No. The flow only uses standard connectors: Excel Online (Business), Office 365 Outlook and Power Automate. A basic shared mailbox needs no license of its own up to 50 GB.
What is the difference between Send As and Send on behalf?
With Send As, the From line shows only the shared mailbox. With Send on behalf, it shows that you sent the email on behalf of the shared mailbox. Both are set under Delegation in the Exchange admin center.
Where do client replies go?
Replies go to the shared mailbox's inbox, not to your own. Team members with access and the sending permission can reply from there.
Why does my flow fail with ErrorSendAsDenied?
The connection account has no Send As permission on that mailbox, often because it only has Full Access. An admin needs to add Send As, and it can take an hour or two to apply.
Can I send each client their own attachments too?
Yes. There is a separate Technologiate video on a mail merge with individual attachments that you can combine with this method.
