群发邮件(邮件不显示在垃圾箱中)

        // <summary>
        /// 发送邮件
        /// </summary>
        /// <param name="fromemail">发件人邮箱</param>
        /// <param name="pwd">发件人密码</param>
        /// <param name="toemail">收件人邮箱</param>
        /// <param name="subject">主题</param>
        /// <param name="body">内容</param>
        /// <returns></returns>
        public static bool SendEmail(string fromemail, string pwd, string toemail, string subject, string body)
        {
            SmtpClient client = new SmtpClient();
            client.Host = "smtp." + fromemail.Remove(0, fromemail.IndexOf("@") + 1);
            client.UseDefaultCredentials = false;
            if (client.Host == "smtp.gmail.com")
                client.EnableSsl = true;
            client.Credentials = new System.Net.NetworkCredential(fromemail, pwd);
            client.DeliveryMethod = SmtpDeliveryMethod.Network;
            MailMessage message = new MailMessage(fromemail, toemail);
            message.Subject = subject;
            message.Body = body;
            message.IsBodyHtml = true;
            message.BodyEncoding = Encoding.UTF8;
            message.Headers.Add("X-Priority", "3");
            message.Headers.Add("X-MSMail-Priority", "Normal");
            message.Headers.Add("X-Mailer", "Microsoft Outlook Express 6.00.2900.2869");
            message.Headers.Add("X-MimeOLE", "Produced By Microsoft MimeOLE V6.00.2900.2869");
            message.Headers.Add("ReturnReceipt", "1");
            try
            {
                client.Send(message);
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

发件人的邮箱QQ邮箱、163邮箱都是可以的，gmail邮箱调用这个方法不行，邮箱的内容是包括HTML格式，有关内容中的字体大小，颜色或者链接等，需转成HTML格式再发送