550 5.4.1: Recipient Address Rejected
Got "550 5.4.1 Recipient Address Rejected"? This Microsoft 365 bounce means your IP or domain is blocked by the recipient's mail server. Here's what causes it and how to get delisted.
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550
5.4.1
Recipient Address Rejected
Very Common
🔢 Enhanced Status Code Breakdown: 5.4.1
| Component | Value | Meaning |
|---|---|---|
| Class | 5 | Permanent failure (Hard bounce) |
| Subject | 4 | Network and routing |
| Detail | 1 | Recipient Address Rejected |
Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.
💬 What This Error Means
The recipient's server has put up a 'No Entry' sign. This usually happens because their security filters have flagged your sending IP address or domain as suspicious. It's especially common with Microsoft 365 when they aren't quite sure about your reputation yet.
Common Causes
- The server is blocking your IP address at the front door
- A security policy at the recipient's company is blocking your domain
- The other server can't verify who you are and has decided to play it safe by rejecting the mail
How to Fix This
- Double-check that the email address is spelled correctly
- If you are sending to a Microsoft 365 user, you may need to use their "delist portal" to clear your reputation
- Make sure your domain is properly authenticated with SPF and DKIM
📚 Official Documentation
Microsoft 365 commonly returns 5.4.1 as "Recipient address rejected: Access denied" for policy-blocked senders. Use the Microsoft delist portal.
📖 Microsoft 365 / Outlook documentation → Browse all Microsoft 365 / Outlook error codes →📋 Real-World Example Messages
These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis.
550 5.4.1 Recipient address rejected: Access denied [AM0P190CA0026.EURP190.PROD.OUTLOOK.COM] 550 5.4.1 [x.x.x.x]: Client host rejected: cannot find your hostname
🔗 Related Error Codes
🔧 Related Diagnostic Tools
These tools can help you diagnose and fix this type of bounce:
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