Custom Anti-Spam Outbound Policy in Microsoft Defender for O365
Custom outbound anti-spam policies in Microsoft Defender for Office 365 protect your organization's reputation by preventing compromised accounts from sending spam, allowing you to set tailored sending limits, configure specific notifications for blocked senders, and automatically restrict suspicious accounts to ensure continuous, reliable email delivery.
Overview
Microsoft 365 allows administrators to manage outgoing emails and control automatic email forwarding to external email addresses using outbound anti-spam policies. Configuring a custom policy helps improve email security and reduces the risk of confidential information being forwarded outside the organization without authorization.
In this article, we will go through the steps to create a custom outbound anti-spam policy in the Microsoft Defender portal and disable automatic external email forwarding. We will also cover how to check the policy settings and test whether the configuration is working correctly.
Importance of Blocking External Automatic Email Forwarding
Automatic email forwarding to external email addresses can sometimes lead to sensitive company information being shared outside the organization. To avoid this, administrators can configure a custom outbound anti-spam policy in Microsoft 365 to control automatic email forwarding and improve email security.
Disabling automatic external forwarding helps protect confidential emails from being forwarded without proper authorization. Users can still send emails to external recipients manually, depending on the organization's other email security policies.
Configuration Steps
Step 1: Sign in to the Microsoft Defender Portal
1. Open a web browser and navigate to https://security.microsoft.com.
2. Sign in using your Microsoft 365 administrator account.
3. Once signed in, you will be redirected to the Microsoft Defender portal.
Step 2: Navigate to Anti-Spam Policies
1. From the left-hand navigation menu, select Email & collaboration.
2. Click Policies & rules.
3. Select Threat policies.
4. Open Anti-spam to view the available anti-spam policies.
Step 3: Create a Custom Outbound Anti-Spam Policy
- On the Anti-spam policies page, locate the Outbound spam filter policy section.
- Select Create policy.
- Choose Outbound if prompted by the portal.
- Enter a suitable name for the policy.
- Click Next to continue.
Step 4: Configure the Policy Scope
- On the Users, groups, and domains page, select the users, groups, or domains to which the policy should apply.
- Click Save to proceed.
Step 5: Disable Automatic External Email Forwarding
- Locate the Forwarding rules section in the policy configuration wizard.
- Find the Automatic forwarding rules setting.
- Open the dropdown menu.
- Select Off – Forwarding is disabled.
- Click Next to continue.
Conclusion
Creating a custom outbound anti-spam policy in Microsoft 365 helps administrators manage automatic email forwarding and keep company emails secure.
By turning off automatic forwarding to external email addresses, organizations can help prevent sensitive information from being shared outside the company without permission. Administrators should also make sure the policy is applied to the correct users and that the settings meet the organization's security needs.
