SMTP 252 Cannot Verify User vs 500 Syntax Error
SMTP 252 (Cannot Verify User) is a 2xx Positive Completion response, while 500 (Syntax Error) is a 5xx Permanent Negative response. 252 indicates that the server cannot verify the user but will accept the message and attempt delivery. This is often returned in response to VRFY when the server intentionally hides user information. In contrast, 500 means that the server could not recognize the command due to a syntax error. The command line was malformed or the command is not recognized by this server.
Description
The server cannot verify the user but will accept the message and attempt delivery. This is often returned in response to VRFY when the server intentionally hides user information.
When You See It
When using the VRFY command to check if a recipient exists. The server refuses to confirm or deny the address, typically as a spam-prevention measure.
How to Fix
No fix needed — the server will still attempt delivery. If you need to verify addresses, contact the mail administrator or rely on bounce-back messages instead.
Description
The server could not recognize the command due to a syntax error. The command line was malformed or the command is not recognized by this server.
When You See It
When you send a command the server does not understand — often due to a typo, unsupported command, or an excessively long line.
How to Fix
Check the command spelling and syntax against the SMTP specification. Ensure the command line does not exceed 512 characters and uses proper CRLF line endings.
Key Differences
252 is a 2xx Positive Completion response, while 500 is a 5xx Permanent Negative response.
SMTP 252: The server cannot verify the user but will accept the message and attempt delivery. This is often returned in response to VRFY when the server intentionally hides user information.
SMTP 500: The server could not recognize the command due to a syntax error. The command line was malformed or the command is not recognized by this server.
You encounter 252 when when using the VRFY command to check if a recipient exists. The server refuses to confirm or deny the address, typically as a spam-prevention measure.
You encounter 500 when when you send a command the server does not understand — often due to a typo, unsupported command, or an excessively long line.
When to Use Which
For 252 (Cannot Verify User): No fix needed — the server will still attempt delivery. If you need to verify addresses, contact the mail administrator or rely on bounce-back messages instead. For 500 (Syntax Error): Check the command spelling and syntax against the SMTP specification. Ensure the command line does not exceed 512 characters and uses proper CRLF line endings.