System.Runtime.InteropServices.COMException: The server rejected one or more recipient addresses. The server response was: 451 http://www.spamhaus.org/query/bl?ip=210.211.164.87

i am sending mail i have this error

 System.Runtime.InteropServices.COMException: The server rejected one or more recipient addresses. The server response was: 451 http://www.spamhaus.org/query/bl?ip=210.211.164.87

 

 

my code is this:;;;;;;;;;;;;;;;;;

 
Dim mailMessage As New MailMessageWith mailMessage.Fields
.Item("http:'schemas.Microsoft.Com/cdo/configuration/sendusing") = 2

.Item("http:'schemas.Microsoft.Com/cdo/configuration/smtpserver") = "mail.sysnetglobal.net"

.Item("http:' ...