SMTP 220 Service Ready vs 252 Cannot Verify User
Both SMTP 220 (Service Ready) and 252 (Cannot Verify User) belong to the 2xx Positive Completion category. 220 indicates that the SMTP server is ready to begin the mail transaction. This greeting is the first response a client receives upon connecting, and it typically includes the server's hostname and software identificati Meanwhile, 252 means 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.
描述
The SMTP server is ready to begin the mail transaction. This greeting is the first response a client receives upon connecting, and it typically includes the server's hostname and software identification.
何时出现
Immediately after establishing a TCP connection to the mail server on port 25, 465, or 587. This is the server's welcome banner confirming it is ready to accept commands.
如何修复
No fix needed — this confirms a successful connection. If you do not receive this greeting, check that the server is running, the port is correct, and no firewall is blocking the connection.
描述
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.
何时出现
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.
如何修复
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.
主要区别
SMTP 220: The SMTP server is ready to begin the mail transaction. This greeting is the first response a client receives upon connecting, and it typically includes the server's hostname and software identificati
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.
You encounter 220 when immediately after establishing a TCP connection to the mail server on port 25, 465, or 587. This is the server's welcome banner confirming it is ready to accept commands.
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.
何时使用哪个
For 220 (Service Ready): No fix needed — this confirms a successful connection. If you do not receive this greeting, check that the server is running, the port is correct, and no firewall is blocking the connection. 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.