using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using MailKit.Security;

namespace Ymobile2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            /*
            MailMessage msg = new MailMessage();
            msg.From = new MailAddress("seedagx16@yahoo.ne.jp", "Yoshikazu Yamamoto");
            msg.To.Add(new MailAddress("seedagx16@yahoo.ne.jp", "Yoshikazu Yamamoto"));
            msg.Subject = "test";
            msg.Body = "This is a test message.";

            SmtpClient sc = new SmtpClient();

            sc.Host = "ymobilesmtp.mail.yahoo.ne.jp";
            sc.Port = 465;
            sc.DeliveryMethod = SmtpDeliveryMethod.Network;
            sc.Credentials = new System.Net.NetworkCredential("seedagx16@yahoo.ne.jp", "Bzc2xgc7Iwada");
            sc.EnableSsl = true;

            sc.Send(msg);
            msg.Dispose();

            textBox1.Text += "メールを送信しました\r\n";
            */

            string host = "ホスト名";
            int port = 465;

            try
            {
                using (var smtp = new MailKit.Net.Smtp.SmtpClient())
                {
                    //第3引数のオプションでTLS(SSL)を使うかどうか指定する
                    smtp.Connect(host, port, SecureSocketOptions.SslOnConnect);
                    smtp.Authenticate("ユーザー名", "パスワード");

                    var mail = new MimeKit.MimeMessage();
                    var builder = new MimeKit.BodyBuilder();

                    mail.From.Add(new MimeKit.MailboxAddress("", "送信者アドレス"));
                    mail.To.Add(new MimeKit.MailboxAddress("", "受信者アドレス"));
                    mail.Subject = "題名:テスト";
                    builder.TextBody = "テストです。";
                    mail.Body = builder.ToMessageBody();

                    smtp.Send(mail);
                    smtp.Disconnect(true);

                    textBox1.Text += "メールを送信しました。\r\n";
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }
    }
}