How to Use a Shared Mailbox with an External Gmail Account in Microsoft 365
Question details
The user wants to grant an external Gmail user access to receive and interact with emails sent to an internal Microsoft 365 shared mailbox.
- Product
- Microsoft 365
- Device & OS
- not provided
- Scenario
- Adding an external or guest user to a shared mailbox in an organizational Microsoft 365 environment.
- Observed behavior
- External accounts like Gmail cannot be added directly as members of a standard Microsoft 365 shared mailbox natively.
Ensure you have Microsoft 365 administrator privileges, as managing shared mailboxes, external forwarding, and Microsoft 365 Groups requires access to the Exchange admin center.
Configure Email Forwarding from the Shared Mailbox
Set up automatic forwarding so emails sent to the shared mailbox are simultaneously delivered to the external Gmail account.
Since external users cannot log directly into a shared mailbox, the easiest workaround is to forward incoming messages to their external address. Ensure your organization's anti-spam policies allow automatic external forwarding before using this method.
Log in to the Microsoft 365 admin center using your administrator credentials.
In the left navigation menu, go to Teams & groups, click on Shared mailboxes, and select the specific shared mailbox you want to configure.
In the mailbox properties pane, scroll down to the Email forwarding section and click Edit.
Toggle the switch to turn on 'Forward all emails sent to this mailbox'. Enter the external Gmail address in the forwarding address field.
Check the box next to 'Keep a copy of forwarded email in this mailbox' so internal users can still view the messages, then click Save.
Use a Microsoft 365 Group with Guest Access
Create a Microsoft 365 Group instead of a shared mailbox, which natively supports adding external email addresses as guest members.
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Frequently Asked Questions
Can I add a Gmail user as a direct member of a shared mailbox?
No, Microsoft 365 does not allow external email addresses to be added as direct members of a standard shared mailbox. You must use workarounds like email forwarding or Microsoft 365 Groups.
Can external users send emails 'As' the shared mailbox?
Generally, no. External guests who receive forwarded emails or participate in a Microsoft 365 Group will reply from their own personal email address (e.g., their Gmail address) rather than the shared mailbox address.
Why are forwarded emails from the shared mailbox not reaching the Gmail account?
This is usually caused by your organization's anti-spam outbound policies blocking automatic forwarding to external domains. A tenant administrator needs to modify the outbound spam filter policy in the Microsoft 365 Defender portal to allow automatic forwarding.
