C#使用QQ、163邮箱发送邮件（新手易懂）

前提准备：以QQ邮件为例，前往QQ个人邮箱开启POP3/SMTP服务(腾讯默认关闭状态），开启后获得授权码，并复制保存好。（使用第三方发送邮件，不必填写QQ密码，而是使用授权码）

POP3/SMTP服务开启流程：依次点击设置---账户---往下滑动可看到该服务

需要引用：

using System.Net.Mail;
using System.Net.Mime;

public class myEmailHelper
{
            /// <summary>
            /// SMTP实例
            /// </summary>
            static System.Net.Mail.SmtpClient client = null;

            /// <summary>
            /// 发送信息
            /// </summary>
            /// <param name="Receiver">邮件接收人</param>
            /// <param name="Subject">邮件主题</param>
            /// <param name="content">邮件内容</param>    
            public  void SendEmail(string Receiver, string Subject, string content)
            {
                if (string.IsNullOrEmpty(Receiver) || string.IsNullOrEmpty(Subject)
                    || string.IsNullOrEmpty(content))
                {
                    throw new ArgumentNullException("SendEmail参数空异常！");
                }
                if (client == null)
                {
                    try
                    {
                        //163发送配置                    
                        //client = new System.Net.Mail.SmtpClient();
                        //client.Host = "smtp.163.com";
                        //client.Port = 25;
                        //client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
                        //client.EnableSsl = true;
                        //client.UseDefaultCredentials = true;


                        //qq发送配置的参数//切EnableSsl必须设置为true  
                        client = new System.Net.Mail.SmtpClient();
                        client.Host = "smtp.qq.com";
                        client.Port = 25;
                        client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
                        client.EnableSsl = true;
                        client.UseDefaultCredentials = false;

                        client.Credentials = new System.Net.NetworkCredential("你的邮箱", "授权码");
                    }
                    catch (Exception ex)
                    {
                        throw ex;
                    }
                }
                try
                {
                    System.Net.Mail.MailMessage Message = new System.Net.Mail.MailMessage();
                    Message.SubjectEncoding = System.Text.Encoding.UTF8;
                    Message.BodyEncoding = System.Text.Encoding.UTF8;
                    Message.Priority = System.Net.Mail.MailPriority.High;

                    Message.From = new System.Net.Mail.MailAddress("你的邮箱", "发送显示名");
                    //添加邮件接收人地址
                    string[] receivers = Receiver.Split(new char[] { ',' });
                    Array.ForEach(receivers.ToArray(), ToMail => { Message.To.Add(ToMail); });

                    Message.Subject = Subject;
                    Message.Body = content;
                    Message.IsBodyHtml = true;
                    client.Send(Message);
                }
                catch (Exception ex)
                {
                    throw ex;
                }
            }
}

 Tips:授权码获得之后一定要先复制好，不然下一次获取需要重新生成，避免多余操作。授权码不区分大小写