sendmail function shows:Syntax error, command unrecognized. The server response was:

Question

while sending mail from particular id i get this error,for rest of all id's its working fine, wat was the prob over here..

Syntax error, command unrecognized. The server response was: status code :0

stack trace:

at System.Net.Mail.SmtpConnection.ConnectAndHandshakeAsyncResult.End(IAsyncResult result) at System.Net.Mail.SmtpClient.ConnectCallback(IAsyncResult result)

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Brief:

System.Net.Mail.SmtpException: Syntax error, command unrecognized. The server response was: at System.Net.Mail.SmtpConnection.ConnectAndHandshakeAsyncResult.End(IAsyncResult result) at System.Net.Mail.SmtpClient.ConnectCallback(IAsyncResult result)

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pls help me out..