Public Class fmTitle

    Private Sub btnValidate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnValidate.Click

        'Declaring the Variables'
        Dim Email As String
        Dim AtSymbol As Integer
        Dim User As String
        Dim Domain As String

        Email = txtEnterEmail.Text.Trim

        If Email.Contains(" ") Then
            MessageBox.Show("Email address can't have spaces", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
            txtEnterEmail.Focus()
            Return
        ElseIf Email.Contains("..") Then
            MessageBox.Show("Email address can't have consecutive periods", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
            txtEnterEmail.Focus()
            Return
        ElseIf Not Email.Contains("@") Then
            MessageBox.Show("Email address must have one '@' symbol", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
            txtEnterEmail.Focus()
            Return
        End If

        AtSymbol = Email.IndexOf("@")

        If Email.Contains("@") Then
            User = Email.Substring(0, AtSymbol)
            Domain = Email.Substring(AtSymbol + 1)
        Elseif
            User = ""
            Domain = ""
        ElseIf Domain.Contains("@") Then
            MessageBox.Show("Email address can't have more than one '@' symbol", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
            txtEnterEmail.Focus()
            Return
        End If

    End Sub

    Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click

        'Closing the program
        Me.Close()

    End Sub
End Class

If System.Text.RegularExpressions.Regex.IsMatch(txtEmail.Text, "^[a-zA-Z][\w\.-]*[a-zA-Z0-9]@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z]$") = False Then
                'email address is not valid
            Else
                'email address is valid

            End If