This is a standard Plesk host with a slightly custom interface.
Use the following format for the cron definition:
/usr/bin/php /var/www/vhosts/yourdomain.com/httpdocs/a/a.php cli/auto
/usr/bin/php /var/www/vhosts/mysite.com/httpdocs/a/a.php cli/auto
This host does not have email catch-all functionality.
This means that incoming emailed subscriptions will only work if you set up an email forwarder (for each autoresponder) in Plesk that will automatically forward messages sent to the autoresponder's subscribe email address to your arpReach mailbox (the mailbox you’ve set in Setup / System Settings / System / Incoming email).