Problem with mail server or code error?

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VB

Hello

I am getting the following error when I try to send emails from my contact form:

Transaction failed. The server response was: Sending address not accepted due to spam filter

Does this imply the mail server itself is preventing me from sending emails?

If it's the server, why does the description of the error say this: 'Please review the stack trace for more information about the error and where
it originated in the code?'

The stack trace looks like this:

[SmtpException: Transaction failed. The server response was: Sending address not accepted due to spam filter]
System.Net.Mail.MailCommand.CheckResponse(SmtpStatusCode statusCode, String response) +1525339
System.Net.Mail.MailCommand.Send(SmtpConnection conn, Byte[] command, MailAddress from, Boolean allowUnicode) +46
System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception) +88
System.Net.Mail.SmtpClient.Send(MailMessage message) +1852
contact.contact_submitted_Click(Object sender, EventArgs e) +599
System.EventHandler.Invoke(Object sender, EventArgs e) +0
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +9628722
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +103
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +35
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1724

This MSDN page https://msdn.microsoft.com/en-us/library/swas0fwc(v=vs.110).aspx?cs-save-lang=1&cs-lang=vb#code-snippet-1 suggests checking the
Status Code 'to find the reason the operation failed' and in my error that would seem to be 1525339 (second line in the Stack Trace), but I can't
find anything on the Net for that code.

Thanks