Magento – How to apply simpler password constraints for customers in magento 2

You can put customers in a new customergroup Not logged In. This way you can easily check if the customer is logged in before.

After password change, update customer group and presto. Side affect is that it will be clearly visible in Magento backend.

From Outside Magento.

If you want to send All Customers Reset Password Email, then below is the code.

//place this before any script you want to calculate time
$time_start = microtime(true);

// MAGENTO START
include('app/bootstrap.php');

use Magento\Framework\App\Bootstrap;
use Magento\Customer\Api\AccountManagementInterface;
use Magento\Customer\Model\AccountManagement;

$bootstrap = Bootstrap::create(BP, $_SERVER);
$objectManager = $bootstrap->getObjectManager();

$state = $objectManager->get('Magento\Framework\App\State');
$state->setAreaCode('frontend');

$_customers = $objectManager->create('Magento\Customer\Api\AccountManagementInterface');
$customerCollection = $objectManager->create('Magento\Customer\Model\ResourceModel\Customer\Collection');
$customerCollection->load();
$i = 0;
foreach ($customerCollection as $customers) {

    $email = $customers->getData('email');

    try {
            $_customers->initiatePasswordReset($email, AccountManagement::EMAIL_RESET);
        } catch (NoSuchEntityException $e) {
            // Do nothing, we don't want anyone to use this action to determine which email accounts are registered.
        } catch (\Exception $exception) {
            echo __('We\'re unable to send the password reset email.');
        }
        echo "<pre>";
        echo $i . " Email :-" . $email . " Mail Sent";
    $i++;
}

echo "<pre>";
echo "Total Customers: " . $i;

$time_end = microtime(true);

//dividing with 60 will give the execution time in minutes other wise seconds
$execution_time = ($time_end - $time_start) / 60;

//execution time of the script
echo "<pre>";
echo 'Total Execution Time:</b> ' . $execution_time . ' Mins';

Hope it helps Magento Community :)