On 04-Sept-2012 the code you see below was executing error free. Today on 06-Sept-2012 it now generates the error message "Recieving Access denied - Invalid HELO name". I have read your 550 access denied article and understand what you are saying. However in this specific case I have a simple SMTP client executing in code using the Microsoft Net.Mail.SmtpClient class library. I cannot see how to get around this problem through any code changes. Any suggestions (not necessarily to the code) but otherwise?



Private Sub btnSend_Click(sender As Object, e As System.EventArgs) Handles btnSend.Click

mail = New Net.Mail.MailMessage()

Try

'create the mail message
Mail.IsBodyHtml = False

'set the addresses
mail.From = New Net.Mail.MailAddress(tbFrom.Text)
mail.To.Add("admin@pentongis.com")

'set the content
mail.Subject = tbSubject.Text
mail.Body = tbMSGBody.Text
mail.DeliveryNotificationOptions = Net.Mail.DeliveryNotificationOptions.OnFailure

If chkMap.Checked Then
Dim a As New Mail.Attachment(tbSnapshot.Text)
mail.Attachments.Add(a)
End If

'send the message - currently fails
smtp = New Net.Mail.SmtpClient("mail.pentongis.com")

smtp.Port = 587
smtp.EnableSsl = False

smtp.DeliveryMethod = Net.Mail.SmtpDeliveryMethod.Network
smtp.UseDefaultCredentials = False

'to authenticate we set the username and password properites on the SmtpClient
smtp.Credentials = New Net.NetworkCredential(tbFrom.Text, tbPassword.Text)

clsAppHelper.MakeCylonGlider(pbMain)
Cylon_Start()

btnCancel.Enabled = True
AddHandler smtp.SendCompleted, AddressOf SendCompletedCallback

Dim userState As String = "test message1"
smtp.SendAsync(mail, userState)

Catch ex As Exception
clsErrorHandler.ShowErrorHandler(ex.ToString())

End Try

End Sub