System.Web.Mail send Mail to Hotmail account

 hello
i have a form in which  user enter his mail id and then we send some information on his mail id.
his mail id used in Bcc. and for FROM and TO i used my domain mail id.
this code works when i entered mailid of  gmail.com or in.com  but  when i am trying to send mail to other account such as hotmail,yahoo,rediffmail its not working.

 

can some body help me.

Thanks

This is my code
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 Public Function fncSendOdrEmail(ByVal strBody As String, ByVal strSubject As String, ByVal strToAddress As String, ByVal bccAddress As String, Optional ByVal strAttachment As String = "", Optional ByVal TOMAIL As String = "") As Integer
        Dim objSMTPMail As New System.Net.Mail.SmtpClient   ' Variable which will send the mail
        ...