External forwarding in Microsoft 365 Exchange Online allows users to automatically forward their emails to an external email address. This feature can be useful, but it also raises security concerns. This knowledgebase article provides step-by-step instructions for enabling external forwarding using both the Exchange Online Admin Center (EAC) and PowerShell. Follow these steps carefully to ensure a smooth and secure setup.

External forwarding is blocked by Microsoft's default outbound-spam policy. 

Table of Contents

Using the Exchange Online Admin Center (EAC)

  Disabling Anti-Spam Outbound Policy for External Mail Forwarding in EAC

Accessing the Exchange Online Admin Center
Enabling External Forwarding for a Mailbox
Disabling External Forwarding for a Mailbox

Using PowerShell

  Disabling Anti-Spam Outbound Policy for External Mail Forwarding in EAC

Connecting to Exchange Online PowerShell
Checking Current External Forwarding Settings
Enabling External Forwarding for a Mailbox
Disabling External Forwarding for a Mailbox

Using the Exchange Online Admin Center (EAC)

 Disabling Anti-Spam Outbound Policy for External Mail Forwarding in EAC

This is a required step to enable external forwarding.

1. Go to security.microsoft.com and log in to the Microsoft 365 security and compliance center with your admin credentials.

2. In the left navigation pane, click on "Policies & rules" and then select "Threat policies."

3. Under "Anti-spam policies," select the "Anti-spam outbound policy" (usually named "Default") that is causing the blockage.

4. Click on "Edit policy settings" to modify the protection settings of the selected anti-spam outbound policy.

5. In the "Automatic forwarding rules" section, you should see "On - Forwarding is enabled."

6. Proceed with disabling the automatic forwarding rule by setting it to "Off."

7. After changing the setting, you will be prompted with the message: "To complete this operation, your organization will need to be set up to support customization. Would you like to do this now?"

8. Respond to the prompt by selecting "Yes" to apply the changes and disable the anti-spam outbound policy for external mail forwarding.

Accessing the Exchange Online Admin Center

To access the Exchange Online Admin Center, follow these steps:

• Log in to the Microsoft 365 admin center: admin.microsoft.com
• In the left navigation pane, click on "Admin centers," then select "Exchange."

Enabling External Forwarding for a Mailbox

To enable external forwarding using EAC, perform the following actions:

• Go to "Recipients" > "Mailboxes" in the Exchange admin center.
• Select the target mailbox and click on the "Mailbox Features" tab.
• Under "Mail flow," click on "View details" next to "Mail forwarding."
• In the "Mail forwarding" window, select "Enable forwarding" and enter the external email address.
• Choose whether to deliver messages to both the mailbox and the forwarding address or just to the forwarding address.
• Click "Save" to apply the changes.

Disabling External Forwarding for a Mailbox

To disable external forwarding using EAC, follow these steps:

• Go to "Recipients" > "Mailboxes" in the Exchange admin center.
• Select the target mailbox and click on the "Mailbox Features" tab.
• Under "Mail flow," click on "View details" next to "Mail forwarding."
• In the "Mail forwarding" window, uncheck "Enable forwarding" and click "Save" to apply the changes.

Using PowerShell

Disabling Anti-Spam Outbound Policy for External Mail Forwarding in EAC

This is a required step to enable external forwarding.

1. Go to security.microsoft.com and log in to the Microsoft 365 security and compliance center with your admin credentials.

2. In the left navigation pane, click on "Policies & rules" and then select "Threat policies."

3. Under "Anti-spam policies," select the "Anti-spam outbound policy" (usually named "Default") that is causing the blockage.

4. Click on "Edit policy settings" to modify the protection settings of the selected anti-spam outbound policy.

5. In the "Automatic forwarding rules" section, you should see "On - Forwarding is enabled."

6. Proceed with disabling the automatic forwarding rule by setting it to "Off."

7. After changing the setting, you will be prompted with the message: "To complete this operation, your organization will need to be set up to support customization. Would you like to do this now?"

8. Respond to the prompt by selecting "Yes" to apply the changes and disable the anti-spam outbound policy for external mail forwarding.

Connecting to Exchange Online PowerShell

To connect to Exchange Online PowerShell, execute the following command:

Checking Current External Forwarding Settings

To check the current external forwarding settings for a specific mailbox, run the following command:

Enabling External Forwarding for a Mailbox

To enable external forwarding for a specific mailbox, use this PowerShell command:

Disabling External Forwarding for a Mailbox

To disable external forwarding for a specific mailbox, use this PowerShell command:

Replace "externaladdress@example.com" with the desired external forwarding address. Proceed with caution, considering the security implications.

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