What does 500 mean?
SMTP 500 indicates a syntax error in the command:
What it means:
The receiving server did not understand the command you sent. The command may be malformed, unsupported, or out of sequence.
Common causes:
Protocol errors: Commands sent incorrectly. Software bugs: Mail client or server issues. Incompatibility: Extended commands not supported. Encoding problems: Character set issues in commands.
Typical message examples:
"500 Syntax error, command unrecognized" "500 Unrecognized command" "500 Error: bad syntax"
Response:
This is typically a sender-side issue. Check your mail server configuration. Review SMTP protocol compliance.
500 says "I don't understand." The problem is in what you sent, not who you sent it to.
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