cannot send email from asp.net

[Verdana]

It works fine for a particular email address, but rest of the emails dont works..following error shows up:\[code\]Server Error in '/RealTimeArsenicDataVisualizer' Application.Mailbox name not allowed. The server response was: From address not verified - see http://help.yahoo.com/l/us/yahoo/mail/original/manage/sendfrom-07.html \[/code\]my code:\[code\] System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient("smtp.mail.yahoo.co.in", 587); client.UseDefaultCredentials = false; client.Credentials = new System.Net.NetworkCredential(emailid, password); client.Port = 587; client.Host = "smtp.mail.yahoo.co.in"; client.EnableSsl = false; object userstate = msg; client.Send(msg);\[/code\]