try

            {

                P2BEmail email = new P2BEmail();

                email.fromEmail = txtfromEmail.Text; //　　QQ邮箱

                email.fromPwd = txtfrompwd.Text;　　  //　　QQ邮箱授权码

                email.emailType = txtemailtype.Text;　　//　　smtp.qq.com

                email.SendEmail(txttoemail.Text, txtsubject.Text, txtbody.Text, "");

                txtmessage.Text = "成功";

            }

            catch (Exception ex)

            {

                txtmessage.Text = ex.Message + ex.StackTrace;

            }

public class P2BEmail

    {

        public string fromEmail = "XX@qq.com";//邮件发送方

        public string fromPwd = "XXXXXXXXXX"; //邮件发送方密码/QQ授权码

        public string emailType = "smtp.qq.com";//邮件类型 smtp.163.com.cn; smtp.qq.com.cn; smtp.126.com.cn;  smtp.sina.com.cn

        /// <summary>

        /// 发送电子邮件

        /// </summary>

        /// <param name="toEmail">接收方电子邮件</param>

        /// <param name="subject">邮件标题</param>

        /// <param name="body">邮件内空</param>

        public void SendEmail(string toEmail, string subject, string body, string attFile)

        {

            MailAddress addrFrom = new MailAddress(fromEmail, fromEmail);

            MailAddress addrTo = new MailAddress(toEmail, toEmail);

            MailMessage mm = new MailMessage(addrFrom, addrTo);

            mm.BodyEncoding = Encoding.UTF8;

            mm.IsBodyHtml = true;

            mm.Subject = subject;

            mm.Body = body;

            if (!string.IsNullOrEmpty(attFile))

            {

                Attachment att = new Attachment(attFile, MediaTypeNames.Application.Octet);

                ContentDisposition cd = att.ContentDisposition;

                cd.CreationDate = File.GetCreationTime(attFile);

                cd.ModificationDate = File.GetLastWriteTime(attFile);

                cd.ReadDate = File.GetLastAccessTime(attFile);

                mm.Attachments.Add(att);//添加附件

            }

            NetworkCredential nc = new NetworkCredential(fromEmail, fromPwd);

            SmtpClient smtp = new SmtpClient(emailType);

            smtp.EnableSsl = true;　　//启用SSl
　　　　　　  //　　随请求一起发送

            smtp.UseDefaultCredentials = false;
　　　　　　  //　　邮件账户凭证

            smtp.Credentials = nc;
　　　　　　　//　　邮件发送方式-网络发送

            smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
　　　　　　　//　　服务器证书验证回调　

            ServicePointManager.ServerCertificateValidationCallback =delegate (Object obj, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors) { return true; };　　

            try

            {

                smtp.Send(mm);

            }

            catch (SmtpFailedRecipientException)

            {

                smtp.Dispose();

                return;

            }

            catch (Exception ex)

            {

                throw ex;

            }

            smtp.Dispose();

        }

    }