501 5.1.3: Invalid Address Syntax
The 501 5.1.3 bounce error means the email address format is invalid. Learn what causes this SMTP error and how to correct address formatting.
Published · Last verified · Maintained by TamingDNS
501
5.1.3
Invalid Address Syntax
Common
🔢 Enhanced Status Code Breakdown: 5.1.3
| Component | Value | Meaning |
|---|---|---|
| Class | 5 | Permanent failure (Hard bounce) |
| Subject | 1 | Address / Destination |
| Detail | 3 | Invalid Address Syntax |
Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.
💬 What This Error Means
The email address you entered looks like it's missing something. It might be missing the '@' symbol, have an extra space, or contain characters that aren't allowed in an email address.
Common Causes
- An extra space at the beginning or end of the address
- Missing the "." in the domain part (like @gmailcom)
- Using characters like parentheses or brackets where they don't belong
- Copy-pasting an address that included the person's name (like "John <[email protected]>")
How to Fix This
- Carefully re-type the address and make sure there are no hidden spaces
- Check that the address follows the standard "[email protected]" format
- If you copy-pasted the address, try typing it in manually instead
📚 Official Documentation
📋 Real-World Example Messages
These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis.
501 5.1.3 Bad recipient address syntax 501 5.1.3 Invalid address format
🔗 Related Error Codes
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