How to manage external email warnings in Outlook using Microsoft 365

Administrators can manage Outlook external email warnings in Office 365 for emails that are received from outside the organization using Exchange mail flow rules. They can create new rules, delete the old ones, and even edit the existing rules directly from the Exchange Admin Center.

The warning in an email allows the members of the organization to identify whether an email is sent from within the organization or from outside. To manage the mail flow rules, you must be an administrator or have the Organization Management role assigned.  In the following sections, we will explore how you can manage the warnings for an external email in Outlook.

Why does Outlook show external email warnings?

Outlook shows a warning when an email matches the conditions of a mail flow rule. Such a warning alerts users that the email was sent from an untrusted source. You must be cautious before you open any attachments or links in the email.

The motive to use an external sender warning in Microsoft 365 is to:

• Prevent users from falling victim to phishing attacks by displaying a warning text that states the email’s origin.
• Remind employees to be cautious while replying to an email or opening an embedded link.
• Help distinguish emails received from within the organization and from external sources.
• Implement a security practice that helps to protect the overall integrity of the organization.

How to add external email warning using Exchange Admin Center

To setup external email warning rule in Outlook using the admin center GUI, follow these steps:

1. Navigate to the Exchange Admin Center home page and log in using your Office 365 credentials.
2. On the left-side panel, click the Mail flow option and select Rules. This section allows you to manage Outlook external email warnings in Office 365
3. In the right-side window, click Add a Rule and choose the Create a new rule option.

4. Provide a name for the new rule. For Apply this rule if value select The recipient.
5. For the next option, choose is external/internal.
6. For the Select recipient location, select the Inside the organization option, and click Save.
7. Click the + (add icon) and choose the value The sender.
8. Same as step 5, choose is internal/external for the next dropdown. And in the window pop up, choose Outside the organization and click Save.
9. For Do the following, choose Apply a disclaimer to the message. Then choose the prepend a disclaimer option for the next field.
10. Click Enter Text and provide the message you want to display. Then, click Save.
11. Then, click Select one link.
12. In the new window, select a fallback option and click Save.
13. Click Next to proceed.
14. Pick a Rule mode, choose a Severity level, and specify other settings as per your need. Then, click Next.
15. Review the conditions and click Finish to create the rule.
16. Office 365 will begin to create the rule. When it's done, you will see a confirmation message.
17. By default, the rule will be disabled. To enable it, go back to the Rule page. Select the rule you just created for external email warning.
18. In the new window pop up, notice the toggle button for the Enable or disable rule option. It will be Disabled. Click on the toggle button to enable it.
19. Wait for a few seconds (minutes if server load is high), the rule Status and toggle button, both will turn to Enabled.

Add external email warning in Outlook using Exchange Management Shell

You can also use the cmdlets to manage Outlook external email warning in Office 365. To setup external email warning rule in Outlook, open Exchange Management Shell (EMS) and connect to Exchange Online. Then, run the following command:

New-TransportRule -Name "External Disclaimer" ` -FromScope NotInOrganization ` -ApplyHtmlDisclaimerLocation Prepend ` -ApplyHtmlDisclaimerText "PASTE THE TEXT YOU

WANT TO DISPLAY BEFORE ANY EXTERNAL EMAIL IN OUTLOOK." ` -

ApplyHtmlDisclaimerFallbackAction Wrap

Note: You must be an admin or at least have the Organization Management permission assigned to run the New-TransportRule cmdlet.

The above command will prefix a disclaimer/message to an email (that matches the condition of the rule) that you receive from a sender that is not in your organization.

How to disable Outlook external email warning in Office 365

If you no longer need a warning rule, you can disable it using the EAC or the EMS. Let’s see how:

Disable external email warning in Outlook using EAC

1. Navigate to EAC > Mail flow > Rules, as you did above.
2. Select the rule you created for handling external warnings.
3. In the window that pops up to the right, click the toggle button that says Enabled.

   Note: If it shows Disabled, don’t click on it.

4. Wait for the status to change to Disabled.

Disable external email warning in Outlook using EMS

• Open the EMS
• Connect to Exchange Online
• Run this command
• Disable-TransportRule -Identity "YOUR-RULE-NAME"

How to change external email warning in Outlook using Exchange Admin Center

After creating a new rule, you can edit its conditions and settings from the admin center. Use the following steps to modify an existing Outlook email warning rule:

• Go to EAC. From the left-navigation menu, click Mail flow and select Rules.
• Select the rule you want to change and click the Edit button.
• Make the changes, then click Save.

How to remove external email warning in Outlook

Using the admin center or the PowerShell commands, you can remove the external email warning in Office 365.

Remove the warning rule using EAC

• Go to EAC. From the left-navigation menu, click Mail flow and select
• Select the rule you want to remove and click the Delete button.
• Click Confirm to delete the rule.

Remove the warning rule using EMS

In the management shell, run the following command:

• Remove-TransportRule -Identity " YOUR-RULE-NAME "

Recovering Exchange database files after malware attacks

The Outlook external email warning can only help in identifying and avoiding suspicious emails. However, they will not help you if your EDB file is already corrupted due to a malware attack. In this case, you need to repair EDB file. The fastest way to restore the server is to recover the database using a backup. However, if you don’t have a backup or the backup itself is affected by viruses, you can use the Microsoft built-in tool, eseutil. Follow these steps to remove the corrupt data:

1. Dismount the database (if not already dismounted due to corruption) by running this command in PowerShell.

   Dismount-Database -Identity "YourDatabaseName"

2. Then, run the eseutil command with the /p switch in the PowerShell

   Note: All the damaged pages will be deleted permanently after running this command

   eseutil /p "YOUR_EDB_FILE_COMPLETE_PATH"

3. Defragment the database with this command:

   eseutil /d "YOUR_EDB_FILE_COMPLETE_PATH"

4. Finally, do an integrity check using New-MailboxRepairRequest or isinteg (for Exchange Server 2010 and earlier versions)

After repairing the EDB file, check its status using the eseutil /mh command. If the .edb is in a clean state, mount the EDB file to the server. But if the command shows the EDB file state as dirty, the eseutil fails due to severe corruption.

In such instances, you must use a professional Exchange database recovery tool. Choose a tool that can repair any level of damage from EDB file, without losing any mailbox items. And most importantly, restore all the files/folders with the original folder structure and metadata.

Our Kernel Exchange Suite software is a one-stop solution to every Exchange Server-related issue. EDB repair, restore deleted mailbox, migrate mailbox across tenants, database backup, etc., the suite can help you with all.

Secure email communication with Microsoft 365 transport rules

The Exchange transport rules help with secure email communication. The fastest way to manage Outlook external email warning in Office 365 is to use the EMS. With a single command, you can create it, disable it, or delete it. And for users who prefer a GUI approach and want more control, use EAC. But make sure you have the required role assigned to manage the mail flow rule. Moreover, since the mail flow rules affect the whole organization, discuss with your teammates before adding or removing a mail flow rule.

Sarthak PoswalTechnical Writer

This article is written by Sarthak Poswal, a technical content writer at Kernel Data Recovery. This content has been reviewed in accordance with our editorial guidelines.