private async void btnSendAsync_Click(object sender, EventArgs e) { Mail.Net.Mailing m = new Mailing(txtUsr.Text, txtPwd.Text, txtSmtpHost.Text, Convert.ToInt32(txtSmtpPort.Text), txtFromAddress.Text, chkSsl.Checked); await m.SendMailAsync(txtRecipients.Text, txtBCC.Text, txtSubject.Text, txtBody.Text, () => { MessageBox.Show("Send complete!"); }, (ex) => { MessageBox.Show(ex.ToString()); }); }