This is not possible with the Joomla mass mail functionality. In order manage the number of email messages sent via Joomla for a specific time frame, you need a custom component to manage emails. It is advisable to to check the official Joomla extensions website for newsletter component that would suit your needs:
http://extensions.joomla.org/extensions/content-sharing/newsletter/
One of the most popular and widely used extensions we could recommend is Acajoom.
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