public class Account
{
    public static List<Account> myAccountList = new List<Account>();
    public string Domain; //this is supposed to be google/skype/facebook
    public string Email;
    public string Username;
    public string Password;

    public Account (string domain, string email, string username, string password)
    {
        Domain = domain;
        Email = email;
        Username = username;
        Password = password;
        myAccountList.Add(new Account(domain, email, username, password)); //constructor calls the new list instance
    }
    private static void SaveToFile()
    {
        System.IO.File.WriteAllLines(@accountdb.txt, myAccountList);
    }
    private static void ReadFromFile() // this is meant to be used as authentication in my main form, it isn't necessary right now..
    {
        System.IO.File.ReadAllLines(@accountdb.txt);
    }
}

private void buttonSave_Click(object sender, EventArgs e)
    {
        string domain, email, username, password;
        domain = comboboxDomain.Text;
        email = textboxEmail.Text;
        username = textboxUsername.Text;
        password = textboxPassword.Text;
        //Checking for correct EMAIL

        if (!textboxEmail.Text.Contains("@") && (!textboxEmail.Text.Contains(".")))
        {
            MessageBox.Show("Invalid Email Format");
        }
        else
        {
            Account account = new Account(domain, email, username, password);
        }
    }