要发送HTML格式邮件，需要设置MailMessage对象的IsBodyHtml属性，设置为true。
类MailMessage在命名空间System.Net.Mail下。
using System.Net.Mail;
发送HTML格式的邮件在HoverTreeTop项目中已经实现，并发送成功。
需依赖于HoverTreeFrame项目的HoverTreeEmail类。
方法为：
public static string HoverTreeSendEmail(string userName, string password, SmtpClient smtpClient, MailMessage mailMessage)
页面截图：
EmailSend.aspx页面：
<h2>发送邮件</h2>
<br />收信人邮箱：<asp:TextBox runat="server" ID="textBox_mail" TextMode="Email" Columns="53" />
<br />标题：<asp:TextBox runat="server" ID="textBox_title" Columns="60" />
<br /><asp:CheckBox runat="server" ID="checkBox_isHtml" Text="是否HTML格式" />
<br />内容：
<br /><asp:TextBox runat="server" ID="textBox_content" TextMode="MultiLine" Rows="10" Columns="70" />
<br /> <asp:Button runat="server" ID="button_send" Text="发送邮件" OnClick="button_send_Click" />
<br />
<asp:Literal runat="server" ID="literal_tips" />
EmailSend.aspx.cs代码：
using System;
using System.Net.Mail;
using HoverTree.HoverTreeFrame.HtNet;
using HoverTreeTop.HtConfig.MyConfig; namespace HoverTreeTop.HoverTree.HoverTreePanel.HTPanel.HEmail
{
public partial class EmailSend : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{ } protected void button_send_Click(object sender, EventArgs e)
{
//使用smtp来发送邮件
//literal_tips.Text = HoverTreeEmail.HoverTreeSendEmail("smtp.hovertree.com", "hello@.mail.hovertree.com", "hewenqi", "hello@mail.hovertree.com", "ht@mail.hovertree.com", "祝你生日快乐！", "生日快乐！天天开心！ -- 何问起");
// literal_tips.Text = HoverTreeEmail.HoverTreeSendEmail(HtSmtpConfig.HtSmtpHost, HtSmtpConfig.HtSmtpUserName, HtSmtpConfig.HtSmtpPassword, HtSmtpConfig.HtSmtpFromEmail, textBox_mail.Text.Trim(), textBox_title.Text, textBox_content.Text); SmtpClient h_smtpClient = new SmtpClient();
h_smtpClient.Host = HtSmtpConfig.HtSmtpHost;
MailMessage h_mailMessage = new MailMessage();
h_mailMessage.From = new MailAddress(HtSmtpConfig.HtSmtpFromEmail);
h_mailMessage.To.Add(textBox_mail.Text.Trim());
h_mailMessage.Subject = textBox_title.Text.Trim();
h_mailMessage.Body = textBox_content.Text;
h_mailMessage.IsBodyHtml = checkBox_isHtml.Checked; literal_tips.Text = HoverTreeEmail.HoverTreeSendEmail(HtSmtpConfig.HtSmtpUserName, HtSmtpConfig.HtSmtpPassword, h_smtpClient, h_mailMessage); if (literal_tips.Text == "")
{
literal_tips.Text = "发送成功！";
textBox_content.Text = "";
textBox_title.Text = "";
textBox_mail.Text = "";
}
}
}
}
用于发送的示例内容：
<html>
<body>
<h2>C#发送html格式的邮件 by 何问起</h2>
<a href="http://hovertree.com/h/bjag/swth6nfh.htm">http://hovertree.com/h/bjag/swth6nfh.htm </a>
<div style="background-color:green;width:200px;height:100px;color:white">何问起 HoverTreeTop</div>
</body>
</html>
参考：http://hovertree.com/h/bjag/swth6nfh.htm