External Email Warning / Disclaimer in Office365

Office 365/Exchange Online/Apply Disclaimer for External Email (Incoming)

This feature displays a clear banner or warning message on emails received from external senders, alerting users that the message originated outside the organization. It helps users quickly identify potentially suspicious emails and reduces the risk of falling victim to phishing or spoofing attempts.

1. Log in to the Exchange Online Admin Center:

- Open a web browser and go to the URL of the Exchange Online Admin Center. https://admin.exchange.microsoft.com

- Log in with an account that has administrative privileges.

For All the Users:

- Expand Mail Flow > Rules > Add Rule > Apply Disclaimers

• Name of the Rule : External Email Disclaimer

• Apply this Rule if : Select The sender is external/Internal > Choose Outside the organization

• And : Select The Recipient is external/Internal > Choose Inside the organization

• Do the Following : Apply a disclaimer to the message > Append a disclimer

• Click on Enter Text

  <table border=0 cellspacing=0 cellpadding=0 align=left width=`"100%`">

  <tr>

  <td style='background:#bba555;padding:5.25pt 5.5pt 5.25pt 1.5pt'></td>

  <td width=`"100%`" style='width:100.0%;background:#ffe599;padding:5.25pt

  3.75pt 5.25pt 11.25pt; word-wrap:break-word' cellpadding=`"7px 5px 7px

  15px`" color=`"#212121`">

  <div><p><span style='font-size:11pt;font-family:Arial,sans-serif;color:

  #212121'>

  <b>CAUTION:</b> This email originated from outside the organization.

  Do not click links or open attachments unless you recognize the sender

  and know the content is safe.

  </span></p></div>

  </td></tr></table>

• Fallback Action : Wrap

• Next : Priority 0

• Rule Mode : Enforce

• Severity: Medium

• Match Sender Address in the Message : Header

• Comments : Implemented for External Spam Email

• Set Rule Conditions (Optional)

  • Add exceptions such as: Users/Groups

• Save and Activate

  • Review your settings

  • Click Save

  • Ensure the rule is turned On

For Specific User:

- Kindly update only the specific setting listed below while keeping all other configurations the same as above.

• And : Select The Recipient is external/Internal > Choose Users/Groups

Using Exchange Online PowerShell

You can also create Rules using PowerShell commands in the Exchange Online Power Shell.

PS Command to Create Rule

New-TransportRule -Name "External Email Warning" -FromScope NotInOrganization -SentToScope InOrganization -ApplyHtmlDisclaimerLocation Prepend -ApplyHtmlDisclaimerText "<div style='color:red;'><strong> Caution:</strong> This email originated from outside the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.</div>" -ApplyHtmlDisclaimerFallbackAction Wrap

Enable-TransportRule -Identity "External Email Warning"

That’s it! By following these steps, you should be able to create new rule for external email disclaimer for your Office 365 Tenant as needed.