C#使用SMTP发送邮件

需要用到的命名空间：

using System.Net.Mail;

using System.IO;

using System.Text.RegularExpressions;

using System.Collections;

using System.ComponentModel;

发送邮件的方法如下：

其中处理附件的代码实现的效果是自动根据文件扩展名获得ContentType值，且发送的附件名与上传的文件名一致。

/// <summary>

/// 发送邮件给相关人

/// </summary>

/// <param name="sendToList">收件人列表(以分号分隔)</param>

/// <param name="attachment">附件路劲（服务器端路劲）</param>

/// <param name="subject">邮件主题</param>

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

/// <param name="sysEmail">使用的系统邮箱</param>

/// <param name="sysEmailPwd">系统邮箱密码</param>

/// <param name="smtpUrl">系统邮箱SMTP的URL</param>

/// <returns>返回空字符串代表成功，否则为错误信息字符串</returns>

public string SendEmail(string sendToList, Hashtable attachment, string subject, string mailBody, 

                        string sysEmail, string sysEmailPwd, string smtpUrl)

{

    try

    {

        string strReturn = "";

        //return strReturn;



        MailMessage mail = new MailMessage();



        sendToList = sendToList.Trim().TrimEnd(';');

        if (sendToList.Length == 0)

        {

            return "收件人地址为空";

        }



        mail.From = new MailAddress(sysEmail);

        foreach (string to in sendToList.Split(';'))

        {

            if (Regex.IsMatch(to, @"\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"))

            {

                mail.To.Add(to);

            }

            else

            {

                strReturn += string.Format("{0}邮箱格式错误，未发送\\n", to);

            }

        }



        if (strReturn == "")

        {

            //mail.IsBodyHtml = true;

            //mail.Body = mailBody.Replace("\n\r", "<br />");

            mail.IsBodyHtml = false;

            mail.Subject = subject;

            mail.Body = mailBody;

            mail.SubjectEncoding = Encoding.GetEncoding("UTF-8");

            mail.BodyEncoding = Encoding.GetEncoding("UTF-8");



            if (attachment.Count > 0)

            {

                //mail.Body = mailBody +"\n\r随邮件带附件：";

                string filePath;

                string fileOldName;

                //FileInfo fileInfo;



                foreach (System.Collections.DictionaryEntry objDE in attachment)

                {

                    filePath = objDE.Key.ToString();

                    fileOldName = objDE.Value.ToString();

                    if (File.Exists(filePath))

                    {

                        //fileInfo = new FileInfo(filePath);

                        //if (fileInfo.Length / 1024 >= 10240)//大于10MB

                        //{

                        //    mail.Body += "大附件：<a href='" + System.Web.HttpContext.Current.Request.Url.Host + "/UploadedFiles/" +

                        //                  filePath.Split(new string[] { "\\UploadedFiles\\" }, StringSplitOptions.None)[1] + "'>" + fileOldName + "</a>";

                        //    continue;

                        //}



                        System.Net.Mime.ContentType contentType = new System.Net.Mime.ContentType();

                        contentType.Name = fileOldName;

                        contentType.MediaType = GetContentTypeForFileName(filePath);

                        Attachment mailAttach = new Attachment(new FileStream(objDE.Key.ToString(), FileMode.Open, FileAccess.Read, FileShare.Read), contentType);

                        //Attachment mailAttach = new Attachment(objDE.Key.ToString());

                        mail.Attachments.Add(mailAttach);

                    }

                }

            }



            SmtpClient smtp = new SmtpClient(smtpUrl);

            smtp.Credentials = new System.Net.NetworkCredential(sysEmail, sysEmailPwd);



            //smtp.Port = 25;

            //smtp.Timeout = 180000;//3分钟,默认为100秒

            //smtp.EnableSsl = false;



            smtp.Send(mail);



            //smtp.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback);

            //smtp.SendAsync(mail, "异步发送邮件");



            mail.Dispose();

        }



        return strReturn;

    }

    catch (Exception ex)

    {

        logger.Error("【邮件发送】异常描述：\t" + ex.Message);

        logger.Error("【邮件发送】异常方法：\t" + ex.TargetSite);

        logger.Error("【邮件发送】异常堆栈：\t" + ex.StackTrace);

    }

}

获取文件ContentType值的方法：

/// <summary>

/// 获取文件ContentType值

/// </summary>

/// <param name="fileName">文件完整路劲</param>

/// <returns>文件ContentType值</returns>

private string GetContentTypeForFileName(string fileName)

{

    string ext = System.IO.Path.GetExtension(fileName);

    using (Microsoft.Win32.RegistryKey registryKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(ext))

    {

        if (registryKey == null)

            return null;

        string value = registryKey.GetValue("Content Type").ToString();

        return (value == null) ? string.Empty : value;

    }

}