转自：http://hi.baidu.com/bluesky_cn/item/8bb060ace834c53f020a4df2
下面用到的邮件账号和密码都不是真实的，需要测试就换成自己的邮件账号。
需要引用：
1usingSystem.Net.Mail;2usingSystem.Text;3usingSystem.Net;
程序代码：
1MailMessage myMail =newMailMessage();//创建邮件实例对象2myMail.From =newMailAddress("");//发送者，要和邮件服务器的验证信息对应，不能随便更改34myMail.To.Add(newMailAddress(""));//接收者5myMail.Subject ="C#发送Email";//邮件标题6myMail.SubjectEncoding = Encoding.UTF8;//标题编码7myMail.Body ="this is a test email!";//邮件内容8myMail.BodyEncoding = Encoding.UTF8;//邮件内容编码9myMail.IsBodyHtml =true;//邮件内容是否支持html10SmtpClient smtp =newSmtpClient();//创建smtp实例对象11smtp.Host ="mail.sina.com";//邮件服务器SMTP12smtp.Port =25;//邮件服务器端口13smtp.Credentials =newNetworkCredential("","123456");//邮件服务器验证信息14smtp.Send(myMail);//发送邮件
使用Gmail邮箱发送邮件示例
1MailMessage myMail =newMailMessage();2myMail.From =newMailAddress("");3myMail.To.Add(newMailAddress(""));4myMail.Subject ="C#发送Email";5myMail.SubjectEncoding =Encoding.UTF8;6myMail.Body ="this is a test email from gmail!<a href='http://www.sina.com.cn'>sina</a>";7myMail.BodyEncoding =Encoding.UTF8;8myMail.IsBodyHtml =true;9SmtpClient smtp =newSmtpClient();10smtp.Host ="smtp.gmail.com";11smtp.Port =587;//Gmail的smtp端口12smtp.Credentials =newNetworkCredential("","123456");13smtp.EnableSsl =true;//Gmail要求SSL连接14smtp.DeliveryMethod = SmtpDeliveryMethod.Network;//Gmail的发送方式是通过网络的方式，需要指定15smtp.Send(myMail);
使用QQ邮箱发送邮件示例
1MailMessage myMail =newMailMessage();2myMail.From =newMailAddress("");3myMail.To.Add(newMailAddress(""));4myMail.Subject ="C#发送Email";5myMail.SubjectEncoding =Encoding.UTF8;6myMail.Body ="this is a test email from QQ!";7myMail.BodyEncoding =Encoding.UTF8;8myMail.IsBodyHtml =true;9SmtpClient smtp =newSmtpClient();10smtp.Host ="smtp.qq.com";11smtp.Credentials =newNetworkCredential("","123456");12smtp.Send(myMail);