码迷,mamicode.com
首页 > Windows程序 > 详细

C#邮件发送问题(一)

时间:2018-04-13 16:22:22      阅读:1029      评论:0      收藏:0      [点我收藏+]

标签:string   简单   nts   必须   编程   tpc   HERE   service   utf-8   

邮件发送需考虑很多因素,包括发送邮件客户端(一般编码实现),发送和接收邮件服务器设置等。如果使用第三方邮件服务器作为发送服务器,就需要考虑该服务器的发送限制,(如发送邮件时间间隔,单位时间内发送邮件数量,是否使用安全连接SSL),同时无论使用第三方还是自己的邮件服务器都还需要考虑接收邮件服务器的限制。为理清思路,下面我们简单回顾电子邮件系统的基本网络结构和邮件发送接收流程。

一、电子邮件系统的基本网络结构

如下图:

技术分享图片

邮件发送接收一般经过以下几个节点:

  • 发送邮件客户端(Mail User Agent, MUA) : Formail, Outlook, Webmail, C# Code, Java Code, etc.
  • 发送邮件服务器(Mail Transfer Agent, MTA) : hMailServer, Exchange, TurboMail, etc.
  • 接收邮件服务器(Mail Transfer Agent, MTA)
  • 接收邮件客户端(Mail User Agent, MUA)

发送过程中客户端与服务器及服务器之间使用SMTP协议,在接收过程中客户端与服务端之间使用POP3或IMAP(POP3的替代协议,支持邮件摘要显示和脱机操作)。邮件发送可简单认为是一种文件传输,但与FTP实时文件传输不同,各邮件服务器会保存邮件文件本身,直至被下一个邮件服务器或客户端接收,类似异步与同步的差别。

由上可知,为顺利发送和接受邮件,客户端设置或编码需要严格适应邮件服务器的要求。对于发送邮件需明确:SMTP服务器地址和端口(默认端口25),是否使用安全连接(SSL),验证凭据(用户和密码),及更加细节的邮件格式,邮件编码方式等;对于接收邮件需明确:POP3或IMAP服务器地址和端口(POP3默认端口110,IMAP默认端口143),是否使用安全连接(SSL),验证凭据(用户和密码)

 

二、C#下发送邮件组件及测试

C#下发送邮件的组件使用较为普遍的有以下三个:System.Net.Mail, OpenSmtp, LumiSoft.Net。下面我们就分别对他们进行测试。

发送邮件至少需要发送邮件服务器信息和邮件信息,因此我们建立Host和Mail两个配置类。

技术分享图片
    public class ConfigHost
    {
        public string Server { get; set; }
        public int Port { get; set; }
        public string Username { get; set; }
        public string Password { get; set; }
        public bool EnableSsl { get; set; }
    }

    public class ConfigMail
    {
        public string From { get; set; }
        public string[] To { get; set; }
        public string Subject { get; set; }
        public string Body { get; set; }
        public string[] Attachments { get; set; }
        public string[] Resources { get; set; }
    }
技术分享图片

同时定义一个统一的接口ISendMail,以方便测试和比较。

技术分享图片
    public interface ISendMail
    {
        void CreateHost(ConfigHost host);
        void CreateMail(ConfigMail mail);
        void CreateMultiMail(ConfigMail mail);
        void SendMail();
    }
技术分享图片

 

1、使用System.Net.Mail

System.Net.Mail属于.Net Framework 的一部分,.Net2.0以后可以使用这个组件。

技术分享图片
    using System.Net.Mail;
    public class UseNetMail : ISendMail
    {
        private MailMessage Mail { get; set; }
        private SmtpClient Host { get; set; }

        public void CreateHost(ConfigHost host)
        {
            Host = new SmtpClient(host.Server, host.Port);
            Host.Credentials = new System.Net.NetworkCredential(host.Username, host.Password);
            Host.EnableSsl = host.EnableSsl;
        }

        public void CreateMail(ConfigMail mail)
        {
            Mail = new MailMessage();
            Mail.From = new MailAddress(mail.From);

            foreach (var t in mail.To)
                Mail.To.Add(t);

            Mail.Subject = mail.Subject;
            Mail.Body = mail.Body;
            Mail.IsBodyHtml = true;
            Mail.BodyEncoding = System.Text.Encoding.UTF8;
        }

        public void CreateMultiMail(ConfigMail mail)
        {
            CreateMail(mail);

            Mail.AlternateViews.Add(AlternateView.CreateAlternateViewFromString("If you see this message, it means that your mail client does not support html.", Encoding.UTF8, "text/plain"));

            var html = AlternateView.CreateAlternateViewFromString(mail.Body, Encoding.UTF8, "text/html");
            foreach (string resource in mail.Resources)
            {
                var image = new LinkedResource(resource, "image/jpeg");
                image.ContentId = Convert.ToBase64String(Encoding.Default.GetBytes(Path.GetFileName(resource)));
                html.LinkedResources.Add(image);
            }
            Mail.AlternateViews.Add(html);

            foreach (var attachment in mail.Attachments)
            {
                Mail.Attachments.Add(new Attachment(attachment));
            }
        }

        public void SendMail()
        {
            if (Host != null && Mail != null)
                Host.Send(Mail);
            else
                throw new Exception("These is not a host to send mail or there is not a mail need to be sent.");
        }
    }
技术分享图片
 
2、使用OpenSmtp
开源的发送邮件组件,可以在这里获得源码。但是OpenSmtp目前不支持SSL。
技术分享图片
    using OpenSmtp.Mail;
    public class UseOpenSmtp : ISendMail
    {
        private MailMessage Mail { get; set; }
        private Smtp Host { get; set; }

        public void CreateHost(ConfigHost host)
        {
            Host = new Smtp(host.Server, host.Username, host.Password, host.Port);
        }

        public void CreateMail(ConfigMail mail)
        {
            Mail = new MailMessage();
            Mail.From = new EmailAddress(mail.From);
            foreach (var t in mail.To)
                Mail.AddRecipient(t, AddressType.To);
            
            Mail.HtmlBody = mail.Body;
            Mail.Subject = mail.Subject;
            Mail.Charset = "UTF-8";
        }

        public void CreateMultiMail(ConfigMail mail)
        {
            CreateMail(mail);
            foreach (var attachment in mail.Attachments)
            {
                Mail.AddAttachment(attachment);
            }
            foreach (var resource in mail.Resources)
            {
                Mail.AddImage(resource, Convert.ToBase64String(Encoding.Default.GetBytes(Path.GetFileName(resource))));            
            }
        }

        public void SendMail()
        {
            if (Host != null && Mail != null)
                Host.SendMail(Mail);
            else
                throw new Exception("These is not a host to send mail or there is not a mail need to be sent.");
        }
技术分享图片

3、使用LumiSoft.Net

LumiSoft.Net是非常强大的开源组件,不仅仅发送邮件,同样也可用于接收邮件,是个人认为最好的开源组件了。在这里可以详细了解LumiSoft.Net组件的命名空间,也可以在这里下载其源码和样例。

技术分享图片
    using LumiSoft.Net.SMTP.Client;
    using LumiSoft.Net.AUTH;
    using LumiSoft.Net.Mail;
    using LumiSoft.Net.MIME;
    public class UseLumiSoft : ISendMail
    {
        private SMTP_Client Host { get; set; }
        private Mail_Message Mail { get; set; }

        public void CreateHost(ConfigHost host)
        {
            Host = new SMTP_Client();
            Host.Connect(host.Server, host.Port, host.EnableSsl);
            Host.EhloHelo(host.Server);
            Host.Auth(Host.AuthGetStrongestMethod(host.Username, host.Password));
        }

        public void CreateMail(ConfigMail mail)
        {
            Mail = new Mail_Message();
            Mail.Subject = mail.Subject;
            Mail.From = new Mail_t_MailboxList();
            Mail.From.Add(new Mail_t_Mailbox(mail.From, mail.From));
            Mail.To = new Mail_t_AddressList();
            foreach (var to in mail.To)
            {
                Mail.To.Add(new Mail_t_Mailbox(to, to));
            }
            var body = new MIME_b_Text(MIME_MediaTypes.Text.html);
            Mail.Body = body; //Need to be assigned first or will throw "Body must be bounded to some entity first" exception.
            body.SetText(MIME_TransferEncodings.Base64, Encoding.UTF8, mail.Body);
        }

        public void CreateMultiMail(ConfigMail mail)
        {
            CreateMail(mail);

            var contentTypeMixed = new MIME_h_ContentType(MIME_MediaTypes.Multipart.mixed);
            contentTypeMixed.Param_Boundary = Guid.NewGuid().ToString().Replace("-", "_");
            var multipartMixed = new MIME_b_MultipartMixed(contentTypeMixed);
            Mail.Body = multipartMixed;

            //Create a entity to hold multipart/alternative body
            var entityAlternative = new MIME_Entity();
            var contentTypeAlternative = new MIME_h_ContentType(MIME_MediaTypes.Multipart.alternative);
            contentTypeAlternative.Param_Boundary = Guid.NewGuid().ToString().Replace("-", "_");
            var multipartAlternative = new MIME_b_MultipartAlternative(contentTypeAlternative);
            entityAlternative.Body = multipartAlternative;
            multipartMixed.BodyParts.Add(entityAlternative);

            var entityTextPlain = new MIME_Entity();
            var plain = new MIME_b_Text(MIME_MediaTypes.Text.plain);
            entityTextPlain.Body = plain;
            plain.SetText(MIME_TransferEncodings.Base64, Encoding.UTF8, "If you see this message, it means that your mail client does not support html.");
            multipartAlternative.BodyParts.Add(entityTextPlain);

            var entityTextHtml = new MIME_Entity();
            var html = new MIME_b_Text(MIME_MediaTypes.Text.html);
            entityTextHtml.Body = html;
            html.SetText(MIME_TransferEncodings.Base64, Encoding.UTF8, mail.Body);
            multipartAlternative.BodyParts.Add(entityTextHtml);

            foreach (string attachment in mail.Attachments)
            {
                multipartMixed.BodyParts.Add(Mail_Message.CreateAttachment(attachment));
            }

            foreach (string resource in mail.Resources)
            {
                var entity = new MIME_Entity();
                entity.ContentDisposition = new MIME_h_ContentDisposition(MIME_DispositionTypes.Inline);
                entity.ContentID = Convert.ToBase64String(Encoding.Default.GetBytes(Path.GetFileName(resource))); //eg.<img src="cid:ContentID"/>
                var image = new MIME_b_Image(MIME_MediaTypes.Image.jpeg);
                entity.Body = image;
                image.SetDataFromFile(resource, MIME_TransferEncodings.Base64);
                multipartMixed.BodyParts.Add(entity);
            }
        }

        public void SendMail()
        {
            if (Host != null && Mail != null)
            {
                foreach (Mail_t_Mailbox from in Mail.From.ToArray())
                {
                    Host.MailFrom(from.Address, -1);
                }
                foreach (Mail_t_Mailbox to in Mail.To)
                {
                    Host.RcptTo(to.Address);
                }
                using (var stream = new MemoryStream())
                {
                    Mail.ToStream(stream, new MIME_Encoding_EncodedWord(MIME_EncodedWordEncoding.Q, Encoding.UTF8), Encoding.UTF8);
                    stream.Position = 0;//Need to be reset to 0, otherwise nothing will be sent;
                    Host.SendMessage(stream);
                    Host.Disconnect();
                }
            }
            else
                throw new Exception("These is not a host to send mail or there is not a mail need to be sent.");
        }
    }
技术分享图片

阅读LumiSoft.Net的源代码,可以看到LumiSoft.Net编程严格遵循了RFC(Request For Comments)定义的协议规范。通过阅读这些源码对于了解RFC和其中关于邮件网络协议规范也是非常有帮助的。如果想查阅RFC文档可以通过这个链接

在上面的代码中MIME_MediaTypes类,MIME_TransferEncodings类和Encoding类(System.Text.Encoding)都是或类似于枚举,设置了邮件内容的编码方式或解析方式,这个几个类从根本上决定了邮件的正常传输和显示。MIME_TransferEncodings类设置了文件传输编码,决定邮件头中的Content-Transfer-Encoding字段的值及其他需要传输编码字段的编码方式(如标题中的多国语言)。MIME_MediaTypes类设置邮件各部分内容的类型,决定邮件中Content-Type字段的值。而Encoding类不用说,决定了charset的值。关于这些设置的具体作用下文还将提到,这里略过。

 

4、测试

下表是通过网络搜集的各大SMTP服务器的配置情况,可以选择使用这些配置进行测试:

服务商 SMTP地址 SMTP端口 EnableSsl
gmail smtp.google.com 25, 465 or 587 true
126 smtp.126.com 25 false
163 smtp.126.com 25 false
hotmail smtp.live.com 25 true
sina smtp.sina.com 25 false
sohu smtp.sohu.com 25 false

新建控制台应用程序,测试发送只包含正文的简单邮件:

技术分享图片
    class Program
    {
        static void Main(string[] args)
        {           var h1 = new ConfigHost()
            {
                Server = "smtp.gmail.com",
                Port = 465,
                Username = "******@gmail.com",
                Password = "******",
                EnableSsl = true
            };
var m1 = new ConfigMail()
            {
                Subject = "Test",
                Body = "Just a test.",
                From = "******@gmail.com",
                To = new string[] { "******@gmail.com" }, 
            };

            var agents = new List<ISendMail>() { new UseNetMail(), new UseOpenSmtp(), new UseLumiSoft() };
            foreach (var agent in agents)
            {
                var output = "Send m1 via h1 " + agent.GetType().Name + " ";
                Console.WriteLine(output + "start");
                try
                {
                    agent.CreateHost(h1);
                    m1.Subject = output;        
                    agent.CreateMail(m1);
                    agent.SendMail();
                    Console.WriteLine(output + "success");
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.Message);
                }
                Console.WriteLine(output + "end");
                Console.WriteLine("-----------------------------------");
            }
            Console.Read();
        }
    }
技术分享图片

通过gmail发送邮件时,OpenSmtp由于不支持SSL发送失败,NetMail使用587端口能够成功发送,LumiSoft使用465端口能够成功发送。查阅Gmail相关文档,描述说Gmail的465端口使用SSL协议,而587端口使用TLS协议,但587是需要STARTTLS命令支持才能提升为TLS。在命令提示符下测试发现的确需要在发送STARTTLS命令后才能使用TLS协议:

技术分享图片
> telnet smtp.gmail.com 587
220 mx.google.com ESMTP o5sm40420786eeg.8 - gsmtp
EHLO g1
250-mx.google.com at your service, [173.231.8.212]
250-SIZE 35882577
250-8BITMIME
250-STARTTLS
250-ENHANCEDSTATUSCODES
250 CHUNKING
AUTH LOGIN
530 5.7.0 Must issue a STARTTLS command first. o5sm40420786eeg.8 – gsmtpSTARTTLS220 
STARTTLS
2.0.0 Ready to start TLS
QUIT
技术分享图片

对于TLS与STARTTLS人们经常搞混,这里找到一篇关于它们的解释,请点击这里

因而LumiSoft如果连接gmail服务器时还需明确发送STARTTLS命令,已经发现LumiSoft有相关方法SMTP_Client.StartTLS(),连接gmail相较其他smtp服务器还是较为复杂些。另外一些服务器要求邮件配置中的Username必须与From相一致,需要特别注意。

 

测试发送带附件和内嵌资源的邮件:

技术分享图片
    class Program
    {
        static void Main(string[] args)
        {
            var h2 = new ConfigHost()
            {
                Server = "smtp.163.com",
                Port = 25,
                Username = "******@163.com",
                Password = "******",
                EnableSsl = false
            };
            var m2 = new ConfigMail()
            {
                Subject = "Test",
                Body = "Just a test. <br/><img src=‘cid:" + Convert.ToBase64String(Encoding.Default.GetBytes("Resource.jpg")) + "‘ alt=‘‘/> ", 
                From = "******@163.com",
                To = new string[] { "******@163.com" }, 
                Attachments = new string[] { @"E:\Test\SendMail\Attachment.pdf" }, 
                Resources = new string[] { @"E:\Test\SendMail\Resource.jpg" } 
            };
          var agents = new List<ISendMail>() { new UseNetMail(), new UseOpenSmtp(), new UseLumiSoft() };
            foreach (var agent in agents)
            {
                var output = "Send m2 via h2 " + agent.GetType().Name + " ";
                Console.WriteLine(output + "start");
                try
                {
                    agent.CreateHost(h2);
                    m2.Subject = output;        
                    agent.CreateMultiMail(m2);
                    agent.SendMail();
                    Console.WriteLine(output + "success");
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.Message);
                }
                Console.WriteLine(output + "end");
                Console.WriteLine("-----------------------------------");
            }
            Console.Read();
        }
    }
技术分享图片

C#邮件发送问题(一)

标签:string   简单   nts   必须   编程   tpc   HERE   service   utf-8   

原文地址:https://www.cnblogs.com/Alex80/p/8820486.html

(0)
(0)
   
举报
评论 一句话评论(0
0条  
登录后才能评论!
© 2014 mamicode.com 版权所有 京ICP备13008772号-2
迷上了代码!