我采用了.net 的自带组件System.Net.Mail发送邮件，主要是在客户注册网站成功的时候发条欢迎邮件，最近邮件无法发送了，看了下腾讯smtp邮件配置，所有的邮件发送都换成ssl了，之前用的是25端口，现在换成了465或587，于是修改代码如下：

MailMessage msgMail = new MailMessage("发件箱", "收件箱", "邮件标题", "邮件内容");
SmtpClient smtp = new SmtpClient("smtp.qq.com", 465);
smtp.EnableSsl = true;
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
smtp.Credentials = new System.Net.NetworkCredential("发件箱", "发件箱登录密码");
try
{
smtp.Send(msgMail);
}
catch (Exception ex)
{
Console.WriteLine("发送完毕......");
}

这样还是不行，报操作已超时错误 在国外的技术网站上看到一句话System.Net.Mail支持Explicit SSL但是不支持Implicit SSL，然后查了下关于这两个模式的资料，我按照我理解的说一下：

Explicit SSL 发起于未加密的25，然后进行一个starttl握手，最终切换到加密的连接。

Implicit SSL 直接从指定的端口发起starttl握手。

既然指定了端口，那么应该就是使用了Implicit SSL，不知道微软什么时候能更新下System.net.mail，System.net.mail能在邮件中嵌入图片的。问题到了这里，那是不是就没有办法利用腾讯邮箱发邮件了呢？答案肯定是否定的，foxmail不就可以配置发送邮件吗？我们可以利用CDO.Message和System.web.mail发送邮件。

C#利用CDO.Message发送邮件

如何引用CDO.Message？ cod.message的引用位置： C:\Windows\System32\cdosys.dll

CDO.Message objMail = new CDO.Message();
try
{
objMail.To = "接收邮件账号";
objMail.From = "发送邮件账号";
objMail.Subject = "subject";//邮件主题string strHTML = @"";
strHTML = strHTML + "这里可以填写html内容";
objMail.HTMLBody = strHTML;//邮件内容
objMail.Configuration.Fields["http://schemas.microsoft.com/cdo/configuration/smtpserverport"].Value = 465;//设置端口
objMail.Configuration.Fields["http://schemas.microsoft.com/cdo/configuration/smtpserver"].Value = "smtp.qq.com";
objMail.Configuration.Fields["http://schemas.microsoft.com/cdo/configuration/sendemailaddress"].Value = "发送邮件账号";
objMail.Configuration.Fields["http://schemas.microsoft.com/cdo/configuration/smtpuserreplyemailaddress"].Value = "发送邮件账号";
objMail.Configuration.Fields["http://schemas.microsoft.com/cdo/configuration/smtpaccountname"].Value = "发送邮件账号";
objMail.Configuration.Fields["http://schemas.microsoft.com/cdo/configuration/sendusername"].Value = "发送邮件账号";
objMail.Configuration.Fields["http://schemas.microsoft.com/cdo/configuration/sendpassword"].Value = "发送邮件账号登录密码";
objMail.Configuration.Fields["http://schemas.microsoft.com/cdo/configuration/sendusing"].Value = 2;
objMail.Configuration.Fields["http://schemas.microsoft.com/cdo/configuration/smtpauthenticate"].Value = 1;
objMail.Configuration.Fields["http://schemas.microsoft.com/cdo/configuration/smtpusessl"].Value = "true";//这一句指示是否使用ssl
objMail.Configuration.Fields.Update();
objMail.Send();
}
catch (Exception ex) { throw ex; }
finally { }
System.Runtime.InteropServices.Marshal.ReleaseComObject(objMail);
objMail = null;

C#利用System.web.mail发送邮件

System.Web.Mail.MailMessage mail = new System.Web.Mail.MailMessage();
try
{
mail.To = "收件人邮箱";
mail.From = "发件人邮箱";
mail.Subject = "subject";
mail.BodyFormat = System.Web.Mail.MailFormat.Html;
mail.Body = "body";
   
mail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate", "1"); //basic authentication
mail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusername", "发件人邮箱"); //set your username here
mail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendpassword", "发件人邮箱密码"); //set your password here
mail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpserverport", 465);//set port
mail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpusessl", "true");//set is ssl
System.Web.Mail.SmtpMail.SmtpServer = "smtp.qq.com";
System.Web.Mail.SmtpMail.Send(mail);
//return true;
}
catch (Exception ex)
{
ex.ToString();
}