🔢 Enhanced Status Code Breakdown: 4.2.1

Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.

💬 What This Error Means

The receiving server is temporarily rejecting your email because you're sending too fast or have sent too many messages recently. This will resolve — retry after a delay.

Common Causes

• Sending volume too high in a short period
• New IP or domain without established sending history
• Daily recipient-side receiving limit exceeded

How to Fix This

• Wait 15–30 minutes and retry
• Reduce sending rate if sending in bulk (throttle to 10–20 emails/min)
• If warming up a new IP, follow a gradual warmup schedule over weeks
• Spread large sends over multiple hours rather than all at once

🏢 Provider-Specific Variations

📋 Real-World Example Messages

These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis.

450 4.2.1 The user you are trying to contact is receiving mail at a rate that prevents additional messages from being delivered. Please resend your message at a later time.

🔗 Related Error Codes

📚 Official Documentation