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Microsoft 365 Tenant-Wide Email Auto Forwarding Setup Guide

This guide explains how to set up tenant-wide email forwarding in Microsoft 365 using PowerShell. This configuration forwards all incoming emails to a CRM or external system while keeping copies in users' original mailboxes.

Prerequisites

Required Permissions

  • Exchange Administrator or Global Administrator role in Microsoft 365
  • Access to Azure Cloud Shell or Windows PowerShell

Important Notes

  • This affects ALL mailboxes in your tenant
  • External forwarding must be enabled at the tenant level first
  • The forwarding email address should be verified and functional

 

Step 1: Enable External Forwarding (REQUIRED)

Before configuring forwarding, you must enable external forwarding in your tenant:

  1. Go to Microsoft 365 Defender Portal: https://security.microsoft.com
  2. Navigate to Email & collaboration > Policies & rules > Threat policies
  3. Click Anti-spam policies
  4. Select Anti-spam outbound policy (Default)
  5. Click Edit protection settings
  6. Change Automatic forwarding from "Automatic - System-controlled" to "On - Forwarding is enabled"
  7. Click Save

⚠️ Critical: Without this step, forwarding will not work and you'll get "Access denied" errors.

 

Step 2: Access PowerShell Environment

Option A: Azure Cloud Shell (Recommended)

  1. Go to https://shell.azure.com
  2. Choose PowerShell when prompted
  3. Wait for initialization to complete

Option B: Windows PowerShell

  1. Right-click Start button > Windows PowerShell (Admin)
  2. Install Exchange module (if not already installed):
Install-Module -Name ExchangeOnlineManagement -Force

 

Step 3: Connect to Exchange Online

Connect-ExchangeOnline
  • You'll be prompted to sign in with your Microsoft 365 admin credentials
  • Complete any multi-factor authentication if required
  • Wait for "Connected to Exchange Online" confirmation

 

Step 4: Check Current Configuration (Optional)

# See how many mailboxes you have

Get-Mailbox -ResultSize Unlimited | Measure-Object

# Check current forwarding status

Get-Mailbox -ResultSize Unlimited | Select-Object DisplayName, ForwardingSmtpAddress, DeliverToMailboxAndForward | Format-Table -AutoSize

 

Step 5: Apply Tenant-Wide Forwarding

Replace your-crm-email@domain.com with your actual forwarding destination:

Get-Mailbox -ResultSize Unlimited | Set-Mailbox -ForwardingSmtpAddress "your-crm-email@domain.com" -DeliverToMailboxAndForward $true

What This Command Does:

  • Applies to ALL mailboxes in your tenant
  • ForwardingSmtpAddress: Sets the external email to forward to
  • DeliverToMailboxAndForward $true: Keeps emails in original inboxes AND forwards copies

 

Step 6: Verify Configuration

Get-Mailbox -ResultSize Unlimited | Select-Object DisplayName, ForwardingSmtpAddress, DeliverToMailboxAndForward | Format-Table -AutoSize

Expected Results:

  • ForwardingSmtpAddress: smtp:your-crm-email@domain.com
  • DeliverToMailboxAndForward: True

 

Step 7: Test the Setup

  1. Send a test email from an external account to any user in your tenant
  2. Verify two things happen:
    • Email appears in the user's inbox normally
    • Forwarded copy arrives at your CRM/forwarding address

 

Troubleshooting

Issue: Emails forward but don't stay in original inboxes

Solution - Reset the configuration:

# Step 1: Clear all forwarding

Get-Mailbox -ResultSize Unlimited | Set-Mailbox -ForwardingSmtpAddress $null -DeliverToMailboxAndForward $false

# Step 2: Wait for processing

Start-Sleep -Seconds 10

# Step 3: Reapply forwarding

Get-Mailbox -ResultSize Unlimited | Set-Mailbox -ForwardingSmtpAddress "your-crm-email@domain.com" -DeliverToMailboxAndForward $true

# Step 4: Verify

Get-Mailbox -ResultSize Unlimited | Select-Object DisplayName, ForwardingSmtpAddress, DeliverToMailboxAndForward | Format-Table -AutoSize

 

Issue: "Access denied" or "5.7.520" errors

  • Cause: External forwarding not enabled at tenant level
  • Solution: Complete Step 1 (Enable External Forwarding) first

Issue: CRM not logging forwarded emails

  • Cause: CRM may require proper forwarding headers
  • Solution: This PowerShell method creates proper forwarded emails that most CRMs recognize

Issue: Command appears stuck

  • Press Ctrl+C to cancel
  • Try processing smaller batches:
# Process first 10 mailboxes as test

Get-Mailbox -ResultSize 10 | Set-Mailbox -ForwardingSmtpAddress "your-crm-email@domain.com" -DeliverToMailboxAndForward $true

 

Managing New Users

For newly created mailboxes, run this command:

Set-Mailbox -Identity "newuser@yourdomain.com" -ForwardingSmtpAddress "your-crm-email@domain.com" -DeliverToMailboxAndForward $true

 

Removing Forwarding (If Needed)

To remove forwarding from all mailboxes:

Get-Mailbox -ResultSize Unlimited | Set-Mailbox -ForwardingSmtpAddress $null -DeliverToMailboxAndForward $false

 

Security Considerations

  • Data Privacy: All emails will be sent to the forwarding address
  • Compliance: Ensure forwarding complies with your organization's data policies
  • Access Control: Limit who has access to the forwarding destination
  • Monitoring: Regularly audit forwarding configurations

Common Use Cases

  • CRM Integration: Forward all customer communications to CRM systems
  • Compliance Archiving: Send copies to compliance/archival systems
  • Backup Systems: Create redundant copies of all communications
  • Monitoring: Forward emails to security monitoring systems

Important Notes

  • Tenant-wide Impact: This affects every mailbox in your organization
  • Immediate Effect: Changes typically take effect within minutes
  • No User Notification: Users won't be notified about forwarding
  • Mail Flow: Original mail flow to users remains unchanged
  • Performance: Minimal impact on email delivery performance

Support

If you encounter issues:

  1. Verify external forwarding is enabled (Step 1)
  2. Check admin permissions
  3. Test with a single mailbox first
  4. Contact your CRM vendor about email processing requirements