Using SmtpClient.SendAsync causes an audit failure of type "Sensitive Privilege Use"

Question

Hi,

The code is:

try { MailMessage message = new MailMessage(); SmtpClient client = new SmtpClient();

            if (this.txtUserName.Text.Trim().Length > 0)
            {
                System.Net.NetworkCredential SMTPUserInfo = new System.Net.NetworkCredential(this.txtUserName.Text.Trim(), this.txtPassword.Text.Trim());
                client.Credentials = SMTPUserInfo;
            }

            message.From = new MailAddress(this.txtFrom.Text.Trim());
            message.To.Add(new MailAddress(this.txtTo.Text.Trim()));
            message.Subject = this.txtTitle.Text.Trim();
            message.Body = this.txtContent.Text.Trim() + "\r\nSMTP Server: " + this.txtSMTPServer.Text.Trim() + "\r\nOrigins: " + Environment.MachineName;

            client.Host = this.txtSMTPServer.Text.Trim();
            client.SendAsync(message, "Token");
            this.lblMessages.Text = "Sending message...";
            message.Dispose();
            client = null;
            GC.Collect();
            return;
        }
        catch (Exception ex)
        {
            this.lblMessages.Text = this.lblMessages.Text + "\r\nError occured\r\n" + ex.ToString();
            return;
        }

It returns no errors however I found an audit failure of type Sensitive Privilege Use in the security audit. I assume that this is preventing the mail to go out.

Test with non .NET based apps send out the mail without issues.

Any iadeas?