Электронная почта активации/ссылка не работает

Я пытаюсь отправить электронное письмо для активации и попросить пользователя активировать свою учетную запись, нажав на предоставленную ссылку. Я настраивал его на основе открытого исходного кода, который я просматривал в Интернете, однако недавно он перестал отправлять электронное письмо без каких-либо ошибок. Вот форма регистрации с функцией отправки электронной почты:

Imports System.Data.SqlClient
Imports System.Data.Sql
Imports System.Data.SqlTypes
Imports System.Data
Imports System.Configuration
Imports System.Net.Mail
Imports System.Net
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts
Imports System.Web.UI.HtmlControls


Public Class WebForm1
Inherits System.Web.UI.Page

Dim boolCar As Object

Private Sub btnSubmit_Click(sender As Object, e As EventArgs) Handles btnSubmit.Click
    If txtEmailAddress.Text.Trim.EndsWith("@umary.edu") Or txtPassword.Text.Trim = txtRetypePassword.Text.Trim Then
        Dim con As New SqlConnection
        Dim cmdEmail As New SqlCommand
        Dim cmdRegistration As New SqlCommand
        Dim EmailCount As Integer = 0

        Try
            con.ConnectionString = "Data Source=SERVERNAME;Initial Catalog=StudentGov;User ID=sa;Password=Password1"
            con.Open()

            cmdEmail = New SqlCommand("SELECT COUNT(UMaryEmail) As EmailCount FROM RegisteredUsers WHERE UMaryEmail='" & txtEmailAddress.Text.Trim & "'", con)
            EmailCount = cmdEmail.ExecuteScalar()

            If EmailCount = 0 Then
                ' Declare database input variables 
                Dim userId As Integer = 0
                Dim firstName As String = txtFirstName.Text
                Dim lastName As String = txtLastName.Text
                Dim hometown1 As String = txtHometown1.Text
                Dim state1 As String = txtState1.Text
                Dim zip1 As String = txtZipCode1.Text
                Dim hometown2 As String = txtHometown2.Text
                Dim state2 As String = txtState2.Text
                Dim zip2 As String = txtZipCode2.Text
                Dim phoneNum As String = txtPhoneNumber.Text
                Dim emailAddress As String = txtEmailAddress.Text
                Dim password As String = txtPassword.Text
                Dim boolCar As Boolean = False
                Dim boolUmary As Boolean = False

                If radYesNo.SelectedIndex = 0 Then
                    boolCar = True
                Else
                    boolCar = False
                End If

                ' Define the command using parameterized query 
                cmdRegistration = New SqlCommand("INSERT INTO RegisteredUsers(FirstName, LastName, Hometown1, State1, ZIP1, Hometown2, State2, ZIP2, PhoneNum, UMaryEmail, Password, Car) VALUES (@txtFirstName, @txtLastName, @txtHometown1, @txtState1, @txtZipCode1, @txtHometown2, @txtState2, @txtZipCode2, @txtPhoneNumber, @txtEmailAddress, @txtPassword, @RadYesNo)", con)

                ' Define the SQL parameter '
                cmdRegistration.Parameters.AddWithValue("@txtFirstName", txtFirstName.Text)
                cmdRegistration.Parameters.AddWithValue("@txtLastName", txtLastName.Text)
                cmdRegistration.Parameters.AddWithValue("@txtHometown1", txtHometown1.Text)
                cmdRegistration.Parameters.AddWithValue("@txtState1", txtState1.Text)
                cmdRegistration.Parameters.AddWithValue("@txtZipCode1", txtZipCode1.Text)
                cmdRegistration.Parameters.AddWithValue("@txtHometown2", txtHometown2.Text)
                cmdRegistration.Parameters.AddWithValue("@txtState2", txtState2.Text)
                cmdRegistration.Parameters.AddWithValue("@txtZipCode2", txtZipCode2.Text)
                cmdRegistration.Parameters.AddWithValue("@txtPhoneNumber", txtPhoneNumber.Text)
                cmdRegistration.Parameters.AddWithValue("@txtEmailAddress", txtEmailAddress.Text)
                cmdRegistration.Parameters.AddWithValue("@txtPassword", txtPassword.Text)
                cmdRegistration.Parameters.AddWithValue("@RadYesNo", boolCar)

                cmdRegistration.ExecuteNonQuery()
                SendActivationEmail(userId)
                Response.Redirect("RegistrationSuccess.aspx")
            Else
                ' Duplicate Email Exist Error Message
                MsgBox("Email address already supplied.")
            End If
            ' Catch ex As Exception (Not needed)
            ' Error Executing One Of The SQL Statements 
        Finally
            con.close()
        End Try
    Else
        ' Throw Error Message 
        MsgBox("Email input error")
    End If
End Sub

   Private Sub SendActivationEmail(userId As Integer)
    Dim sqlString As String = "Server=SERVERNAME;Database=StudentGov;UId=sa;Password=Password1;"
    Dim ActivationCode As String = Guid.NewGuid().ToString()
    Dim ActivationUrl As String = Server.HtmlEncode("http://localhost:63774/ActivateAccount.aspx?userId=" & FetchUserId(txtEmailAddress.ToString) & "&txtEmailAddress=" & txtEmailAddress.ToString & "&ActivationCode=" & ActivationCode.ToString)
    Using con As New SqlConnection(sqlString)
        Using sqlCmd As New SqlCommand("UPDATE RegisteredUsers SET UserId = '" + userId.ToString + "', ActivationCode = '" + ActivationCode.ToString + "' WHERE UMaryEmail='" + txtEmailAddress.Text + "';")
            Using sda As New SqlDataAdapter()
                sqlCmd.CommandType = CommandType.Text
                sqlCmd.Parameters.AddWithValue("@UserId", userId)
                sqlCmd.Parameters.AddWithValue("@ActivationCode", ActivationCode)
                sqlCmd.Connection = con
                con.Open()
                sqlCmd.ExecuteNonQuery()
                con.Close()
            End Using
        End Using
    End Using
    Using mm As New MailMessage("****@outlook.com", txtEmailAddress.Text)
        mm.Subject = "Account Activation"
        Dim body As String = "Hello " + txtFirstName.Text.Trim() + ","
        body += "<br /><br />Please click the following link to activate your account"
        body += "<br /><a href='" & ActivationUrl & "'>Click here to activate your account.</a>"
        body += "<br /><br />Thanks"
        mm.Body = body
        mm.IsBodyHtml = True
        Dim smtp As New SmtpClient()
        smtp.Host = "smtp.live.com"
        smtp.EnableSsl = True
        Dim NetworkCred As New NetworkCredential("****@outlook.com", "****")
        smtp.UseDefaultCredentials = True
        smtp.Credentials = NetworkCred
        smtp.Port = 587
        Try
            smtp.Send(mm)
        Catch ex As Exception
            MsgBox("Email was not sent")
        End Try
    End Using
End Sub

Private Function FetchUserId(emailAddress As String) As String
    Dim cmd As New SqlCommand()
    Dim con As New SqlConnection("Data Source=SERVERNAME;Initial Catalog=StudentGov;User ID=sa;Password=Password1")

    cmd = New SqlCommand("SELECT UserId FROM RegisteredUsers WHERE UMaryEmail=@txtEmailAddress", con)
    cmd.Parameters.AddWithValue("@txtEmailAddress", emailAddress)
    If con.State = ConnectionState.Closed Then
        con.Open()
    End If
    Dim userId As String = Convert.ToString(cmd.ExecuteScalar())
    con.Close()
    cmd.Dispose()
    Return userId
End Function
End Class

А вот и страница активации аккаунта:

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration


Public Class ActivateAccount
Inherits System.Web.UI.Page

Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
    If Not Page.IsPostBack Then
        ActivateMyAccount()
    End If
End Sub


Private Sub ActivateMyAccount()
    Dim con As New SqlConnection()
    Dim cmd As New SqlCommand()

    Try
        con.ConnectionString = "Data Source=CISWEB\UMCISSQL2008;Initial Catalog=StudentGov;User ID=sa;Password=Password1"
        If (Not String.IsNullOrEmpty(Request.QueryString("UserId"))) And (Not String.IsNullOrEmpty(Request.QueryString("UMaryEmail"))) Then

            'approve account by setting Is_Approved to 1 i.e. True in the sql server table
            cmd = New SqlCommand("UPDATE RegisteredUsers SET AccountActivated=1 WHERE UserId=@UserId AND UMaryEmail=@txtEmailAddress", con)
            cmd.Parameters.AddWithValue("@UserId", Request.QueryString("UserId"))

            cmd.Parameters.AddWithValue("@txtEmailAddress", Request.QueryString("UMaryEmail"))
            If con.State = ConnectionState.Closed Then
                con.Open()

            End If
            cmd.ExecuteNonQuery()
            Response.Write("You account has been activated. You can <a href='SignIn.aspx'>Sign in</a> now! ")

        End If
    Catch ex As Exception
        ScriptManager.RegisterStartupScript(Me, Me.[GetType](), "Message", "alert('Error occured : " & ex.Message.ToString() & "');", True)
        Return
    Finally
        con.Close()
        cmd.Dispose()
    End Try
End Sub
End Class

Как вы, наверное, уже поняли, я сбит с толку. Поскольку я не получаю сообщений об ошибках, я не знаю, почему функция SendActivationEmail больше не работает. Кто-нибудь помогите пожалуйста! :(