How Do I Set Up An External Email Warning In Outlook?

If your organization’s users get a lot of spam emails, setting up an external email warning for Office 365/Microsoft 365 email accounts can help your users differentiate between genuine and phishing emails quickly and reduce the risk of a user accidentally falling for a spam email.

Below is a step-by-step guide to setting up an external email warning for Microsoft 365/Office 365 email users:

  1. Navigate to Office.com and sign in using your Microsoft 365 credentials
  2. Open the app launcher and click Admin
  3. Open the Exchange Admin Center
  4. Click mail flow
  5. On the rules page, click “+”, then click Create a new rule…
  6. Name the rule and fill in the form
  7. Click Save and send yourself an email from an external email address to confirm its working

There is no way to set this up within the Outlook application. You have to set up an external email warning through the Microsoft 365 Exchange admin center. With that in mind, you’ll need to be set up as an Exchange admin or Global admin on Microsoft 365 to follow the steps and set up an external email warning.

Here’s the step-by-step process with screenshots so you can follow along and set up an external email warning for your organization’s Office 365/Microsoft 365 email users. Click here to skip to step 6 if you just want the screenshot that shows you how you should fill in the new mail flow rule.

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How To Set Up An External Email Warning In Exchange Admin Center

In this blog post, I’m going to demonstrate how you can set up an external email warning in Exchange Admin Center. It’s a fairly simple process, although you need to follow each step carefully.

To follow the walkthrough in this blog post, you’ll need to be an Exchange admin or Global admin. If you aren’t, you’ll need your Microsoft 365/Office 365 admin to give you the appropriate privileges.

Step-By-Step [With Screenshots]: Setting up an external email warning in Exchange admin center

Following the step-by-step walkthrough below, you can set up an external email warning in the Exchange admin center.

  1. Navigate to Office.com and sign in using your Microsoft 365 credentials
  2. Open the app launcher and click Admin
  3. Open the Exchange Admin Center
  4. Click mail flow
  5. On the rules page, click “+”, then click Create a new rule…
  6. Name the rule and fill in the form [screenshot with example of how the new rule form should look completed]
  7. Click Save and send yourself an email from an external email address to confirm its working

Here’s a demonstration of the entire process including screenshots so you can follow along.

1. Navigate to Office.com and sign in using your Microsoft 365 credentials

Remember that you will need to be a Microsoft 365 Exchange admin or global admin to follow the steps I’m demonstrating here. If you are neither, you’ll need to ask your global admin to assign your user account the appropriate permissions.

2. Open the app launcher and click Admin

Once you’re signed into your Microsoft 365 account, open the app launcher and click Admin.

If the Admin application isn’t showing in the app launcher, it means you don’t have the appropriate permissions.

3. Open the Exchange Admin Center

4. Click mail flow

Mail flow is the section of the Exchange admin center that lets you:

  • Create and modify rules
  • Set up message tracing
  • Set up and configure accepted domains
  • Set up and configure connectors

Click mail flow and it will automatically open up the rules page that you need to be on to create the external message warning.

5. On the rules page, click “+”, then click Create a new rule…

When you click the “+” symbol, it will open up a dropdown menu. Select the option Create a new rule… to open up the window where you create the rule.

6. Name the rule and fill in the form [screenshot with example of how the new rule form should look completed]

First things first, name the rule so you can easily identify and modify it once it’s set up. As you’ll see on the screenshot above, I’ve named our demonstration rule “External email warning message”.

Click the dropdown under “Apply this rule if…” and click The sender is located… — this will open another pop up where you need to select Outside the organization.

Then click More options… [bottom left of the window as shown in the screenshot below]. This will allow you to add another condition.

Click add condition, and then click The recipient… then is external/internal. Then select Inside the organization.

Under “Do the following…”, open the dropdown menu, hover over “Apply a disclaimer to the message…”, and click prepend a disclaimer.

Click Enter text and then enter the following code — you can copy and paste this into the text box and it will be functional without any tweaking:

<p><div style="background-color:#FFEB9C; width:100%; border-style: solid; border-color:#9C6500; border-width:1pt; padding:2pt; font-size:10pt; line-height:12pt; font-family:'Calibri'; color:Black; text-align: left;"><span style="color:#9C6500"; font-weight:bold;>CAUTION:</span> This email originated from outside of the organisation. Do not click links or open attachments unless you recognize the sender and know the content is safe.</div><br></p>

Click OK. Next, click Select one and choose “Wrap”.

Now you should have something looking exactly like this.

7. Click Save and send yourself an email from an external email address to confirm its working

Once you’ve filled everything in, click Save.

At this point, you might want to wait around 10 – 20 minutes. It can sometimes take a little while for a new rule to come into action.

After you’ve waited a few minutes, send yourself an external email — from your personal email account for example — and wait for the email to come through to your organization email. You should see the message appear before the body of the email as demonstrated in the screenshot below.

If you’re seeing the message, you’re all done! This will display above all external emails you get organization-wide.

If the external warning message isn’t displaying, troubleshoot by returning to the walkthrough above and making sure you’ve followed each step carefully and correctly. If you’re still having trouble, leave a comment below and we’ll help out.

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Jack Mitchell

Jack Mitchell has been the Operations manager at telecoms and MSP Optionbox for more than 4 years. He has played a crucial role in the company, from marketing to helpdesk, and ensures that the IT requirements of over 300 clients are continuously met. With his innate passion for technology and troubleshooting and a particular interest in Apple products, Jack now delivers the most comprehensive tech guides to make your life easier. You can connect with Jack on LinkedIn.

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