Adapting Mail within Opencart

Hello

We want to be able to send bulk emails to customers between specific dates within the Mail client in Opencart.
As it currently stands you have to type customers in manually.
When the two sets of dates are entered it will put the customers within theses dates in automatically, we can then send emails to those customers to suggest them to leave feedback and offer them 10% discount.

If any one knows of a free or paid for extension like this please suggest it.

Thank you

Opencart version 1.5.5.1

If no extensions do exists for such request, I would suggest posting this enquiry in the Commercial Support section of the forum to get this done as a custom job. It is doubtful a free extension could be found on the marketplace for a server specific cron task.