using System.Collections.Generic;

using System.Text;
using System.Net;
using System.Net.Mail;

        try
        {
            //编码暂硬性规定为GB2312 
            Encoding encoding = Encoding.GetEncoding(936);
            MailMessage Message = new MailMessage(
            new MailAddress("自己的邮箱", "5", encoding),//第一个是发信人的地址，第二个参数是发信人
            new MailAddress(TextBox1.Text));//收信人邮箱

            Message.SubjectEncoding = encoding;
            Message.Subject =TextBox2.Text;//标题
            Message.BodyEncoding = encoding;
            Message.Body = TextBox3.Text; //主体
            SmtpClient smtpClient = new SmtpClient("smtp.163.com");//信箱服务器
            smtpClient.Credentials = new NetworkCredential("自己的邮箱用户名", "自己的邮箱密码");//信箱的用户名和密码
            smtpClient.Timeout = 999999;
            smtpClient.Send(Message);
        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
        }