How to Fix Shared Mailbox Sending Permissions in Microsoft 365

Summary

This guide helps you troubleshoot and resolve: How to Fix Shared Mailbox Sending Permissions in Microsoft 365. Follow the steps below to fix the issue.

Common Causes

Shared mailboxes in Microsoft 365 allow multiple team members to access a single email address, such as [email protected] or [email protected]. A common issue occurs when staff members can open the shared mailbox and read messages, but receive an error when attempting to send emails from that address. This usually happens because the Send As or Send on Behalf permissions have not been correctly assigned to the user account. This guide explains how to resolve shared mailbox sending permissions for your organisation.

Quick Fix Steps

1. Confirm you have global administrator or exchange administrator privileges in Microsoft 365.
2. Sign in to the Microsoft 365 admin centre.
3. Navigate to Teams & groups > Shared mailboxes.
4. Select the shared mailbox from the list.
5. Review and assign the Send As or Send on Behalf permissions to the affected staff members.
6. Ask the user to restart Outlook or Outlook on the web and test sending a message.

Detailed Instructions

Assigning Send As Permissions

Send As allows a user to send email that appears to come directly from the shared mailbox address. Recipients will not see the individual staff member's name in the sender field.

1. Sign in to the Microsoft 365 admin centre using an administrator account.
2. In the left-hand navigation menu, select Teams & groups, then choose Shared mailboxes.
3. Click on the shared mailbox you need to modify to open its properties pane.
4. Select the Mailbox permissions tab.
5. Under Send As, select Edit.
6. Choose Add permissions.
7. Search for the staff member who needs sending rights and select their name from the results.
8. Select Add, then select Save changes.

Assigning Send on Behalf Permissions

Send on Behalf allows a user to send email from the shared mailbox, but recipients will see that the message was sent on behalf of the shared mailbox by the individual staff member.

1. Sign in to the Microsoft 365 admin centre.
2. Go to Teams & groups > Shared mailboxes.
3. Open the shared mailbox and select the Mailbox permissions tab.
4. Under Send on Behalf, select Edit.
5. Select Add permissions.
6. Search for and select the required user.
7. Select Add, then select Save changes.

Permission changes in Microsoft 365 can take up to 60 minutes to replicate across all servers. Ask the affected user to wait at least one hour before testing if the change does not work immediately.

Troubleshooting

User Still Cannot Send After Permissions Are Assigned

• Ensure the user has restarted Microsoft Outlook. Desktop clients often cache permissions and require a restart to recognise new rights.
• If using Outlook on the web, sign out and sign back in to refresh the session.
• Confirm the user has Full Access to the shared mailbox. Without Full Access, sending permissions may not function as expected.
• Check that the shared mailbox has a valid license assigned if it exceeds the free 50 GB storage limit.

Error: "You Do Not Have Permission to Send to This Recipient"

• Verify that the correct permission type was assigned. Send As and Send on Behalf are not interchangeable.
• Check for any mail flow rules or transport rules in the Exchange admin centre that might be blocking messages from the shared mailbox.
• Ensure the user account is not blocked from sending mail due to suspicious activity or a compromised password.

Only assign sending permissions to staff who genuinely require them. Granting Send As rights broadly increases the risk of unauthorised emails being sent from your organisation's shared addresses.

If you have followed these steps and staff members still cannot send from the shared mailbox, Open a Ticket with our Brisbane support team for further assistance.

Still Having Issues?