Asynchronously sending Emails in Vb.net?

Question

While sending the email using async getting error.

Public Async Function SendEmail(ByVal EmailToIds As String, ByVal Subject As String, ByVal Message As String, Optional ByVal EmailCcIds As String = "", Optional ByVal MailAttachment As String = "", Optional ByVal FromEmailType As Integer = 0, Optional EmailBccIds As String = "") As Task
Dim EmailPwd() As String
Dim FromEmail, Password As String
'Dim objSmtp As SmtpClient
Dim objMail As MailMessage
Dim objAttachment As Attachment
Try
EmailPwd = GetEmailPassword(FromEmailType).Split("|")
FromEmail = EmailPwd(0)
Password = EmailPwd(1)
objMail = New MailMessage
objMail.From = New MailAddress(FromEmail)
objMail.Subject = Subject
objMail.IsBodyHtml = True
objMail.Body = Message
objMail.To.Add(EmailToIds)
   If Len(EmailCcIds) > 0 Then
      objMail.CC.Add(EmailCcIds)
   End If
   If Len(EmailBccIds) > 0 Then
      objMail.Bcc.Add(EmailBccIds)
   End If
   If MailAttachment <> "" Then
      objAttachment = New Attachment(MailAttachment)
      objMail.Attachments.Add(objAttachment)
   End If
Using objSmtp = New SmtpClient()
   objSmtp.Host = ConfigurationSettings.AppSettings("SmtpClient")
   objSmtp.DeliveryMethod = SmtpDeliveryMethod.Network
   objSmtp.UseDefaultCredentials = False
   objSmtp.Credentials = New NetworkCredential(FromEmail, Password)
   objSmtp.Port = 587
   objSmtp.EnableSsl = True
   ServicePointManager.ServerCertificateValidationCallback = Function(s As Object, certificate As X509Certificate, chain As    X509Chain, sslPolicyErrors As SslPolicyErrors) True
   Await objSmtp.SendMailAsync(objMail)
End Using
Catch ex As Exception
    throw rx
End Try
End Function

Error : Failure Sending Mail.

 

Kindly help for the same.