VB.NET发送电子邮件（通过使用SmtpClient类）
以下代码已通过VS2008测试。

    ''' <summary>
    ''' 通过SmtpClient类发送电子邮件
    ''' </summary>
    ''' <param name="ReceiveAddressList">收件人地址列表</param>
    ''' <param name="Subject">邮件主题</param>
    ''' <param name="Content">邮件内容</param>
    ''' <param name="AttachFile">附件列表Hastable。KEY=文件名,Value文件路径</param>
    Private Function SendMail(ByVal ReceiveAddressList As List(Of String),ByVal Subject As String,ByVal Content As String,_
                 Optional ByVal AttachFile As Hashtable = Nothing) As Boolean
      Dim i As Integer
      'SMTP客户端
      Dim smtp As New System.Net.Mail.SmtpClient("SMTP.163.COM")
      'smtp.Host = "smtp.163.com"    'SMTP服务器名称
      '发件人邮箱身份验证凭证。 参数分别为 发件邮箱登录名和密码
      smtp.Credentials = New System.Net.NetworkCredential("邮箱账户","邮箱密码")
      '创建邮件
      Dim mail As New System.Net.Mail.MailMessage()
      '主题编码
      mail.SubjectEncoding = System.Text.Encoding.GetEncoding("GB2312")
      '正文编码
      mail.BodyEncoding = System.Text.Encoding.GetEncoding("GB2312")
      '邮件优先级
      mail.Priority = System.Net.Mail.MailPriority.Normal
      '以HTML格式发送邮件,为false则发送纯文本邮箱
      mail.IsBodyHtml = True
      '发件人邮箱
      mail.From = New System.Net.Mail.MailAddress("发件人邮箱")

      '添加收件人,如果有多个,可以多次添加
      If ReceiveAddressList.Count = 0 Then Return False
      For i = 0 To ReceiveAddressList.Count - 1
        mail.To.Add(ReceiveAddressList.Item(i))
      Next

      '邮件主题和内容
      mail.Subject = Subject
      mail.Body = Content

      '定义附件,参数为附件文件名,包含路径,推荐使用绝对路径
      If Not AttachFile Is Nothing AndAlso AttachFile.Count <> 0 Then
        For Each sKey As String In AttachFile.Keys
          Dim objFile As New System.Net.Mail.Attachment(AttachFile.Item(sKey))
          '附件文件名,用于收件人收到附件时显示的名称
          objFile.Name = sKey
          '加入附件,可以多次添加
          mail.Attachments.Add(objFile)
        Next
      End If

      '发送邮件
      Try
        smtp.Send(mail)
        MessageBox.Show("邮件发送成功！")
        Return True
      Catch
        MessageBox.Show("邮件发送失败！")
        Return False
      Finally
        mail.Dispose()
      End Try
    End Function