/// <summary>

        /// 发送邮件(支持Html发送，支持添加一个附件)

        /// </summary>

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

        /// <param name="email">收件人地址</param>

        /// <param name="content">邮件内容</param>

        /// <param name="filepath">文件的相对路径</param>

        public static void SendEmail(string subject, string email,string content,string filepath=null)

        {

            var message = new MimeMessage();

            //发信人

            message.From.Add(new MailboxAddress("发信人姓名", "发信人邮箱"));

            //收信人

            message.To.Add(new MailboxAddress("", email));

            //标题

            message.Subject = subject;

            //产生一个支持Html的TextPart

            var body = new TextPart(TextFormat.Html)

            {

                Text = content

            };

            //先产生一个

            var multipart = new Multipart("mixed");

            //添加正文内容

            multipart.Add(body);

            if (!string.IsNullOrWhiteSpace(filepath))

            {

                //生产一个绝对路径

                //filepath = "Upload//NewsPhoto//readme.txt";

                var absolutePath = Path.Combine(_hostingEnv.WebRootPath, string.Format(filepath));

                //附件

                var attachment = new MimePart()

                {

                    //读取文件(只能用绝对路径)

                    ContentObject = new ContentObject(File.OpenRead(absolutePath), ContentEncoding.Default),

                    ContentDisposition = new ContentDisposition(ContentDisposition.Attachment),

                    ContentTransferEncoding = ContentEncoding.Base64,

                    //文件名字

                    FileName = Path.GetFileName(absolutePath)

                };

                //添加附件

                multipart.Add(attachment);

            }

            //正文内容

            message.Body = multipart;

            using (var client = new SmtpClient())

            {

                //连接到Smtp服务器

                client.Connect("smtp服务器地址", 端口, false);

                //登陆

                client.Authenticate("账号", "密码");

                //发送

                client.Send(message);

                //断开

                client.Disconnect(true);

            }

        }