private void pn_mailS_Click(object sender, EventArgs e)
{
M_Email mail = new M_Email();
mail.MdiParent = this;
mail.Show();
pn_mail.Hide();
}
private void M_email_Click(object sender, EventArgs e)
{
M_Email mail = new M_Email();
mail.MdiParent = this;
mail.Show();
M_email.Enabled = false;
}
