Yes, indeed there is a limit of 250 emails per hour per domain. If you reach your throttle limit, the subsequent email will be rejected at the SMTP level. If you are sending more than 250 emails per hour, and would like the limit removed you must have a dedicated IP address at $2/month and all outgoing email will be sent via this address. Your domain limit will then be removed.
Please contact our helpdesk via email or submit a support ticket via the client portal for this account change.