Mail Sending From C#

This Code for Mail Sending From C#.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Net.Mail;
namespace wfaDemo
{
public partial class frmMail : Form
{
public frmMail()
{
InitializeComponent();
}
private void txtPort_KeyPress(object sender, KeyPressEventArgs e)
{
if (!Char.IsDigit(e.KeyChar))
e.Handled = true;
}
private void txtUsername_Leave(object sender, EventArgs e)
{
Regex mRegxExpression;
if (txtUsername.Text.Trim() != string.Empty)
{
mRegxExpression = new Regex(@"^([a-zA-Z0-9_\-])([a-zA-Z0-9_\-\.]*)@(\[((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}|((([a-zA-Z0-9\-]+)\.)+))([a-zA-Z]{2,}|(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\])$");
if (!mRegxExpression.IsMatch(txtUsername.Text.Trim()))
{
MessageBox.Show("E-mail address format is not correct.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
txtUsername.Focus();
}
}
}
public void Clear()
{
txtUsername.Clear();
txtPassword.Clear();
txtPort.Clear();
txtPort.Clear();
txtTo.Clear();
txtCc.Clear();
txtBcc.Clear();
txtSubject.Clear();
txtSMTP.Clear();
rtxtBody.Clear();
}
private void btnSend_Click(object sender, EventArgs e)
{
try
{
MailMessage mail = new MailMessage();
SmtpClient SmtpServer = new SmtpClient(txtSMTP.Text);
mail.From = new MailAddress(txtUsername.Text.ToLower());
if ((txtTo.Text != null) && (txtTo.Text != string.Empty))
{
string[] multiRec = txtTo.Text.Split(';');
foreach (string to in multiRec)
{
if (to.Trim().Length > 0)
{
mail.To.Add(new MailAddress(to));
}
}
//mail.To.Add("To Email Address");
}
if ((txtCc.Text != null) && (txtCc.Text != string.Empty))
mail.CC.Add(txtCc.Text);
if ((txtBcc.Text != null) && (txtBcc.Text != string.Empty))
mail.Bcc.Add(txtBcc.Text);
mail.Subject = txtSubject.Text;
mail.Body = rtxtBody.Text;
SmtpServer.Port = int.Parse(txtPort.Text);
SmtpServer.Credentials = new System.Net.NetworkCredential(txtUsername.Text.ToLower(), txtPassword.Text);
if (chkSSL.Checked == true)
SmtpServer.EnableSsl = true;
else
SmtpServer.EnableSsl = true;
SmtpServer.Send(mail);
MessageBox.Show("Mail Send Successfully");
Clear();
}
catch (Exception x)
{
MessageBox.Show("Error : " + x.ToString());
}
}
}
}