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Email at Scale - How to Suppress Auto-Replies in Exchange

Email at Scale uses a dedicated IP address to send high-volume campaigns. This guide shows you how to prevent automatic replies (like Out of Office messages) from being sent back to your organization.

Before You Begin

You need:

  • Admin access to the Microsoft 365 Admin Center
  • Your dedicated IP address (provided during Email at Scale setup or available from support@contactmonkey.com)

Create a Mail Flow Rule in Exchange

  1. Sign in to the Microsoft 365 Admin Center
  2. Under Admin centers, click Exchange
  3. Select Mail Flow from the left-hand menu
  4. Click Rules
  5. Click Add a rule → Create a new rule
  6. Name your rule (example: "Suppress Auto Replies for Email at Scale")
  7. Under Apply this rule if, select the following:
    • First drop-down: The sender
    • Second drop-down: IP address is in any of these ranges or exactly matches
    • Enter your dedicated IP address
    • Click Add, then Save
  8. Under Do the following, select the following:
    • First drop-down: Modify the message properties
    • Second drop-down: Set a message header
    • Header name: X-Auto-Response-Suppress
    • Value: OOF, DR, RN, NRN
  9. Check Stop processing more rules to ensure this rule takes precedence
  10. Add exceptions if needed for specific scenarios
  11. Click next
  12. Review, then click Finish
Image 2025-11-28 at 10.40.51 AM

Test Your Configuration

Send a test email to verify the rule works correctly:

  1. Send an email using the Send & Track button in ContactMonkey (not Send Test)
  2. Ensure your email uses Individual tracking
  3. Confirm no auto-replies are received

Important: Microsoft Exchange sends only one Out of Office reply per recipient per day. To test multiple times in one day, update the recipient's Out of Office message content between tests.

What the Rule Does

The X-Auto-Response-Suppress header prevents these automatic responses:

  • OOF: Out of Office messages
  • DR: Delivery Receipts
  • RN: Read Notifications
  • NRN: Non-Read Notifications

Important Notes

  • This rule only applies to emails sent using Email at Scale tracking
  • Emails sent with Overall tracking are not affected by this rule
  • Verify your dedicated IP address is correct before saving the rule
  • This configuration does not affect other email functionalities

See Also