public partial class frmSend : Form
{
    public frmSend()
    {
        InitializeComponent();
    }
    //對郵件內容進行編碼
    private static string Base64Encode(string str)
    {
        return Convert.ToBase64String(Encoding.UTF8.GetBytes(str));
    }

    private void SendEmail(MailMessage message)
    {
        message.Subject = Base64Encode(txtSubject.Text);    //設置發送郵件的主題
        message.Body = Base64Encode(txtContent.Text);       //設置發送郵件的內容
        //實例化SmtpClient郵件發送類對象
        SmtpClient client = new SmtpClient(txtServer.Text, Convert.ToInt32(txtPort.Text));
        //設置用于驗證發件人身份的憑據
        client.Credentials = new System.Net.NetworkCredential(txtName.Text, txtPwd.Text);
        //發送郵件
        client.Send(message);
    }

    private void frmSend_Load(object sender, EventArgs e)
    {
        txtServer.Text = Dns.GetHostName();
    }

    private void btnSend_Click(object sender, EventArgs e)
    {
        try
        {
            if (validateEmail(txtSend.Text))
            {
                //設置郵件發送人和接收人
                MailMessage message = null;
                if (txtTo.Text.IndexOf(",") != -1)
                {
                    string[] strEmail = txtTo.Text.Split(',');
                    string sumEmail = "";
                    for (int i = 0; i < strEmail.Length; i++)
                    {
                        sumEmail = strEmail[i];
                        message = new MailMessage(new MailAddress(txtSend.Text), new MailAddress(sumEmail));
                        SendEmail(message);
                    }
                }
                else
                {
                    message = new MailMessage(new MailAddress(txtSend.Text), new MailAddress(txtTo.Text));
                    SendEmail(message);
                }
                MessageBox.Show("發送成功");
            }
        }
        catch
        {
            MessageBox.Show("發送失敗!");
        }
    }

    private void frmSend_FormClosing(object sender, FormClosingEventArgs e)
    {
        DialogResult = DialogResult.OK;
    }

    #region  驗證輸入為Email
    /// <summary>
    /// 驗證輸入為Email
    /// </summary>
    /// <param name="str"></param>
    /// <returns></returns>
    public static bool validateEmail(string str)
    {
        return Regex.IsMatch(str, @"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*");
    }
    #endregion
}

partial class frmSend
{
    /// <summary>
    /// 必需的設計器變量。
    /// </summary>
    private System.ComponentModel.IContainer components = null;

    /// <summary>
    /// 清理所有正在使用的資源。
    /// </summary>
    /// <param name="disposing">如果應釋放托管資源，為 true；否則為 false。</param>
    protected override void Dispose(bool disposing)
    {
        if (disposing && (components != null))
        {
            components.Dispose();
        }
        base.Dispose(disposing);
    }

    #region Windows 窗體設計器生成的代碼

    /// <summary>
    /// 設計器支持所需的方法 - 不要
    /// 使用代碼編輯器修改此方法的內容。
    /// </summary>
    private void InitializeComponent()
    {
        this.txtContent = new System.Windows.Forms.TextBox();
        this.txtSubject = new System.Windows.Forms.TextBox();
        this.txtPort = new System.Windows.Forms.TextBox();
        this.txtServer = new System.Windows.Forms.TextBox();
        this.txtPwd = new System.Windows.Forms.TextBox();
        this.txtName = new System.Windows.Forms.TextBox();
        this.txtTo = new System.Windows.Forms.TextBox();
        this.txtSend = new System.Windows.Forms.TextBox();
        this.label8 = new System.Windows.Forms.Label();
        this.label7 = new System.Windows.Forms.Label();
        this.label6 = new System.Windows.Forms.Label();
        this.label5 = new System.Windows.Forms.Label();
        this.label4 = new System.Windows.Forms.Label();
        this.label3 = new System.Windows.Forms.Label();
        this.label2 = new System.Windows.Forms.Label();
        this.label1 = new System.Windows.Forms.Label();
        this.btnSend = new System.Windows.Forms.Button();
        this.SuspendLayout();
        // 
        // txtContent
        // 
        this.txtContent.Location = new System.Drawing.Point(23, 143);
        this.txtContent.Multiline = true;
        this.txtContent.Name = "txtContent";
        this.txtContent.ScrollBars = System.Windows.Forms.ScrollBars.Vertical;
        this.txtContent.Size = new System.Drawing.Size(519, 100);
        this.txtContent.TabIndex = 7;
        // 
        // txtSubject
        // 
        this.txtSubject.Location = new System.Drawing.Point(88, 94);
        this.txtSubject.Name = "txtSubject";
        this.txtSubject.Size = new System.Drawing.Size(186, 21);
        this.txtSubject.TabIndex = 6;
        // 
        // txtPort
        // 
        this.txtPort.Location = new System.Drawing.Point(356, 62);
        this.txtPort.Name = "txtPort";
        this.txtPort.Size = new System.Drawing.Size(186, 21);
        this.txtPort.TabIndex = 5;
        // 
        // txtServer
        // 
        this.txtServer.Location = new System.Drawing.Point(88, 63);
        this.txtServer.Name = "txtServer";
        this.txtServer.Size = new System.Drawing.Size(186, 21);
        this.txtServer.TabIndex = 4;
        // 
        // txtPwd
        // 
        this.txtPwd.Location = new System.Drawing.Point(356, 34);
        this.txtPwd.Name = "txtPwd";
        this.txtPwd.PasswordChar = '*';
        this.txtPwd.Size = new System.Drawing.Size(186, 21);
        this.txtPwd.TabIndex = 3;
        // 
        // txtName
        // 
        this.txtName.Location = new System.Drawing.Point(88, 35);
        this.txtName.Name = "txtName";
        this.txtName.Size = new System.Drawing.Size(186, 21);
        this.txtName.TabIndex = 2;
        // 
        // txtTo
        // 
        this.txtTo.Location = new System.Drawing.Point(356, 6);
        this.txtTo.Name = "txtTo";
        this.txtTo.Size = new System.Drawing.Size(186, 21);
        this.txtTo.TabIndex = 1;
        // 
        // txtSend
        // 
        this.txtSend.Location = new System.Drawing.Point(88, 6);
        this.txtSend.Name = "txtSend";
        this.txtSend.Size = new System.Drawing.Size(186, 21);
        this.txtSend.TabIndex = 0;
        // 
        // label8
        // 
        this.label8.AutoSize = true;
        this.label8.Location = new System.Drawing.Point(15, 121);
        this.label8.Name = "label8";
        this.label8.Size = new System.Drawing.Size(65, 12);
        this.label8.TabIndex = 12;
        this.label8.Text = "郵件內容：";
        // 
        // label7
        // 
        this.label7.AutoSize = true;
        this.label7.Location = new System.Drawing.Point(15, 93);
        this.label7.Name = "label7";
        this.label7.Size = new System.Drawing.Size(65, 12);
        this.label7.TabIndex = 11;
        this.label7.Text = "郵件主題：";
        // 
        // label6
        // 
        this.label6.AutoSize = true;
        this.label6.Location = new System.Drawing.Point(290, 65);
        this.label6.Name = "label6";
        this.label6.Size = new System.Drawing.Size(53, 12);
        this.label6.TabIndex = 14;
        this.label6.Text = "端口號：";
        // 
        // label5
        // 
        this.label5.AutoSize = true;
        this.label5.Location = new System.Drawing.Point(21, 65);
        this.label5.Name = "label5";
        this.label5.Size = new System.Drawing.Size(53, 12);
        this.label5.TabIndex = 17;
        this.label5.Text = "服務器：";
        // 
        // label4
        // 
        this.label4.AutoSize = true;
        this.label4.Location = new System.Drawing.Point(278, 37);
        this.label4.Name = "label4";
        this.label4.Size = new System.Drawing.Size(77, 12);
        this.label4.TabIndex = 16;
        this.label4.Text = "發件人密碼：";
        // 
        // label3
        // 
        this.label3.AutoSize = true;
        this.label3.Location = new System.Drawing.Point(9, 37);
        this.label3.Name = "label3";
        this.label3.Size = new System.Drawing.Size(77, 12);
        this.label3.TabIndex = 15;
        this.label3.Text = "發件人名稱：";
        // 
        // label2
        // 
        this.label2.AutoSize = true;
        this.label2.Location = new System.Drawing.Point(290, 9);
        this.label2.Name = "label2";
        this.label2.Size = new System.Drawing.Size(53, 12);
        this.label2.TabIndex = 13;
        this.label2.Text = "收件人：";
        // 
        // label1
        // 
        this.label1.AutoSize = true;
        this.label1.Location = new System.Drawing.Point(21, 9);
        this.label1.Name = "label1";
        this.label1.Size = new System.Drawing.Size(53, 12);
        this.label1.TabIndex = 18;
        this.label1.Text = "發件人：";
        // 
        // btnSend
        // 
        this.btnSend.Location = new System.Drawing.Point(217, 251);
        this.btnSend.Name = "btnSend";
        this.btnSend.Size = new System.Drawing.Size(116, 23);
        this.btnSend.TabIndex = 9;
        this.btnSend.Text = "發送";
        this.btnSend.UseVisualStyleBackColor = true;
        this.btnSend.Click += new System.EventHandler(this.btnSend_Click);
        // 
        // frmSend
        // 
        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.ClientSize = new System.Drawing.Size(551, 279);
        this.Controls.Add(this.txtContent);
        this.Controls.Add(this.txtSubject);
        this.Controls.Add(this.txtPort);
        this.Controls.Add(this.txtServer);
        this.Controls.Add(this.txtPwd);
        this.Controls.Add(this.txtName);
        this.Controls.Add(this.txtTo);
        this.Controls.Add(this.txtSend);
        this.Controls.Add(this.label8);
        this.Controls.Add(this.label7);
        this.Controls.Add(this.label6);
        this.Controls.Add(this.label5);
        this.Controls.Add(this.label4);
        this.Controls.Add(this.label3);
        this.Controls.Add(this.label2);
        this.Controls.Add(this.label1);
        this.Controls.Add(this.btnSend);
        this.Name = "frmSend";
        this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
        this.Text = "使用SMTP服務發送不帶附件的郵件";
        this.Load += new System.EventHandler(this.frmSend_Load);
        this.FormClosing += new System.Windows.Forms.FormClosingEventHandler(this.frmSend_FormClosing);
        this.ResumeLayout(false);
        this.PerformLayout();

    }

    #endregion

    private System.Windows.Forms.TextBox txtContent;
    private System.Windows.Forms.TextBox txtSubject;
    private System.Windows.Forms.TextBox txtPort;
    private System.Windows.Forms.TextBox txtServer;
    private System.Windows.Forms.TextBox txtPwd;
    private System.Windows.Forms.TextBox txtName;
    private System.Windows.Forms.TextBox txtTo;
    private System.Windows.Forms.TextBox txtSend;
    private System.Windows.Forms.Label label8;
    private System.Windows.Forms.Label label7;
    private System.Windows.Forms.Label label6;
    private System.Windows.Forms.Label label5;
    private System.Windows.Forms.Label label4;
    private System.Windows.Forms.Label label3;
    private System.Windows.Forms.Label label2;
    private System.Windows.Forms.Label label1;
    private System.Windows.Forms.Button btnSend;
}