The software does not restrict the number of emails sent per batch. It is unlimited. It is your ISP(Internet Service Provider), which restricts the number of emails sent per batch.
To get around this ISP restriction, EmailMerge Pro provides you with a feature to choose the number of emails you want to send at certain intervals. This feature is available at the Configure sending options step (second last step) of the wizard . Clicking the Send all e-mails at once at this step will allow you to configure sending options.