500: SMTP Syntax Error

The 500 SMTP error means the receiving server received a malformed command. Learn what causes this and how your email provider should fix it.

Published · Last verified · Maintained by TamingDNS

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Permanent Failure (Hard Bounce)
SMTP Code
500
Category
SMTP Syntax Error
Frequency
Common

💬 What This Error Means

The two servers are having a 'misunderstanding.' Your mail server sent a command that the recipient's server didn't recognize or couldn't process correctly. This is usually a technical glitch in the way the servers are talking to each other.

Common Causes

  • A brief technical error or "syntax" mistake in the conversation between servers
  • One of the servers is using an outdated or non-standard way of talking
  • A temporary glitch in the server software

How to Fix This

  • Try sending your email again. It might have been a one-time glitch
  • If it keeps happening, the problem is likely with your email provider's server settings

📚 Official Documentation

↗ RFC 5321: SMTP

📋 Real-World Example Messages

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

500 Syntax error, command unrecognized
500 5.5.2 Syntax error

🔗 Related Error Codes

501
Bad Parameter or Argument
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