Could not open input mailpoet-cron.php

Mailpoet suggests to use this cron command:

php /var/www/qbxxxxx/data/www/domain.ext/cms/wp-content/plugins/mailpoet/mailpoet-cron.php /var/www/qbxxxxx/data/www/domain.ext/cms/

With frequency: */1 * * * *

With this command cron sends every minute an email with this content:

Could not open input file: /var/www/qbxxxxx/data/www/domain.ext/cms/wp-content/plugins/mailpoet/mailpoet-cron.php

mailpoet-cron.php is present at that location.

Emails are not sent because of this problem.
How can this be solved?