This depends greatly on the plan selected. Please note that the 2 offerings for Email Marketer Pro are not the only offerings available. We can customize hardware to meet the desired results in terms of emails per hour.
We have conducted several sending tests which averaged 2,000 emails per hour using the cron sending method as opposed to the “popup” sending method on a server with only 512mb of memory and a single core processor. This 2,000 emails per 1/2GB of memory can be used as a metric. If you wish to send 10,000 emails per hour, then a machine with multiple cores, multiple processors, and approx. 4GB of memory or more will be sufficient.