add_filter("retrieve_password_message", "custom_password_reset", 99, 4);
function custom_password_reset($message, $key, $user_login, $user_data )    {

    $message = __('Someone has requested a password reset for the following account:') . "<br><br>";
    $message .= network_home_url( '/' ) . "<br><br>";
    $message .= sprintf(__('%s'), $user_data->user_email) . "<br><br>";
    $message .= __('If this was a mistake, just ignore this email and nothing will happen.') . "<br><br>";
    $message .= __('To reset your password use the link below:') . "<br><br>";
    $message .= "<a href=".network_site_url("wp-login.php?action=rp&key=$key&login=" . rawurlencode($user_login), 'login') .">Click here to reset your password</a><br><br>";
    $message .= "Or copy and paste this link into your browser:<br><br>".network_site_url("wp-login.php?action=rp&key=$key&login=" . rawurlencode($user_login), 'login')."<br><br>";

    return $message;
}