temporary rate limiting

Question

We are currently experiencing temporary rate limiting on the following IP: 5.231.118.2

Error observed: 451 4.7.651 – Temporarily rate limited due to IP reputation (S3114) Following this, we have taken immediate corrective actions: • Significantly reduced sending volume and concurrency • Restricted sending to highly engaged and permission-based recipients only • Verified full authentication (SPF, DKIM, DMARC all aligned and passing) • Implemented stricter sending controls and monitoring • Ensured consistent and gradual sending patterns We understand that this is a reputation-based limitation and not a block. However, we would appreciate if you could review the current status of this IP following these improvements. We are committed to maintaining compliant and responsible sending practices. Thank you for your time and assistance. Best regards

Answer 1

Hello,

Your request needs to be submitted here: https://sender.office.com/ Only that team and that channel can assist you.

Answer 2

451 4.7.651 with code S3114 indicates that Outlook.com/Microsoft 365 is temporarily throttling traffic from the IP because of its current sending reputation. This is a temporary restriction, not a permanent block, and is automatically reevaluated by Microsoft systems.

Key points and actions based on current behavior and best practices:

1. Automatic reevaluation
   • When suspicious activity is detected from an IP, Microsoft temporarily restricts mail while it is being evaluated.
   • After messages are evaluated and determined to be acceptable, the restriction is removed automatically; there is no manual override path documented for individual IPs.
2. Continue the corrective actions already in place
   • Maintain reduced sending volume and concurrency and avoid sudden spikes in traffic.
   • Keep sending only to highly engaged, permission-based recipients and ensure list hygiene (remove invalid/bouncing addresses and honor unsubscribes).
   • Maintain correct SPF, DKIM, and DMARC alignment for all mail.
   • Monitor complaint rates and bounce rates; high complaint or hard-bounce rates are a primary driver of poor reputation.
3. Manage sending rate and patterns
   • Spread bulk sends over time instead of sending large bursts.
   • Keep a consistent, gradual sending pattern so the IP can build or rebuild a positive reputation.
4. New or recently changed IPs
   • If the IP is new or recently started sending higher volumes, expect a ramp-up period while reputation is built. During this time, some throttling is normal until the IP establishes a history of non-spam traffic.
5. Ongoing monitoring
   • Continue monitoring delivery, throttling responses, and engagement metrics. As reputation improves and complaint/bounce rates remain low, throttling should lessen and eventually stop.

There is no documented support channel to request a manual review or expedited removal of this specific rate limit; the system lifts the restriction after it determines that traffic from the IP is safe and compliant over time.

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References:

• External senders - Troubleshoot email sent to Microsoft 365
• Sender Support in Outlook.com
• Best practices for email marketing
• Troubleshoot outbound sending limits and blocked users in Exchange Online