smtp problem (system.net.mail)

I've written email pro in asp .net

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim mail As New MailMessage()

Try

'set the addresses

mail.From = New MailAddress("name@company.com")

mail.To.Add(youname@comapny.com)

'set the content

mail.Subject = "This is an email"

mail.Body = "this is the body content of the email."

'send the message

Dim smtp1 As New SmtpClient("mail.company.com", 25)

Dim basicAuthenticationInfo As New System.Net.NetworkCredential("name", "pass")

smtp1.UseDefaultCredentials = False

Catch ex As Exception

End Try

End Sub

i got this error

Transaction failed. The server response was: The IP Address of the sender (202.46.122.38) was found in a DNS blacklist database and was therefore refused.

pls advise me