Eicra Host allows you to send up to 200 emails per hour, we do this to prevent spam. Whenever your domain exceeds the limit, you will get bounce back emails with the following information:
Domain example.com has exceeded the max emails per hour (227/200 (113%)) allowed. Message discarded.
This error is derived from an hourly monitoring system, where any blocked domains are allowed to send email again at the top of every hour.
So keep in mind that, one domain can only send 200 emails in one hour. If your domain has 20 accounts, every account can send less or equal to 20 emails.
If you need to send more than that, you need to upgrade your package to Dedicated or VPS server.