Email Code using your gmail account

Imports System.Net.Mail
Imports System.Net
Imports Main
Imports System.Data.SqlClient

Partial Class Teacher_Email_Class
    Inherits System.Web.UI.Page

    Protected Sub LinkButton1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles LinkButton1.Click
        Dim sql As String
        TextBox1.Text = 

            sql = Select email FROM Registration WHERE  ' You query
        Dim Conn As String = ConfigurationManager.ConnectionStrings(ConnectionString).ConnectionString
        Dim SQLConn As New SqlConnection(Conn)
        Dim cmd As New SqlCommand(sql, SQLConn)
        Dim reader As SqlDataReader

        SQLConn.Open()
        reader = cmd.ExecuteReader()
        While reader.Read()
            If reader.HasRows Then
                TextBox1.Text &= reader(email) & ; 
            End If
        End While
        reader.Close()
        SQLConn.Close()
    End Sub

    Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim arr() As String
        arr = TextBox1.Text.Split(;)
        Dim mailmessage As New Mail.MailMessage()
        mailmessage.From = New MailAddress(myemil@gmail.com, Title)
        mailmessage.ReplyTo = New MailAddress(TextBox4.Text, Session(FName))
        'To 
        For Each s As String In arr
            mailmessage.To.Add(New MailAddress(s))
        Next
        'mailmessage.Subject = DropDownList1.SelectedValue
        mailmessage.Subject = TextBox3.Text
        TextBox2.Text = SingleQuoteToDoubleQuote(TextBox2.Text)
        mailmessage.Body = TextBox2.Text
        If FileUpload1.HasFile Then
            mailmessage.Attachments.Add(New Attachment(FileUpload1.PostedFile.FileName))
        End If
        Dim smtp As SmtpClient = New SmtpClient()
        Try
            'Your SMTP Server
            smtp.Host = smtp.gmail.com 

            'SSL Settings depending on your Server
            smtp.EnableSsl = True


            'Creadentials for the Serve
            Dim NetworkCred As Net.NetworkCredential = New System.Net.NetworkCredential()

            'Your Email
            NetworkCred.UserName = yourusername

            'Your Password
            NetworkCred.Password = yourpassword

            smtp.UseDefaultCredentials = True
            smtp.Credentials = NetworkCred

            'Port No of the Server 
            smtp.Port = 587
            smtp.Send(mailmessage)
            
        Catch ex As Exception
            Label1.Text = ex.Message
           
        Finally
            smtp = Nothing
            mailmessage = Nothing
        End Try
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim Conn As String = ConfigurationManager.ConnectionStrings(ConnectionString).ConnectionString
        Dim SQLConn As New SqlConnection(Conn)
        Dim sql As String = SELECT email FROM Registration WHERE UID=' _
        & Session(UserName) & ' ORDER BY UID ASC
        Dim cmd As New SqlCommand(sql, SQLConn)
        Dim reader As SqlDataReader

        SQLConn.Open()
        reader = cmd.ExecuteReader()
        reader.Read()

        TextBox4.Text = reader(email)
        reader.Close()
        SQLConn.Close()
    End Sub
End Class