I Need to know if it is possible to resend the notifications for a particular period which are already sent from SM?
It requires that your application that sends the emails leave them in eventout. Then you can change the status of those emails so they will be resent but you also need to make sure the mail applications pointer is reset.
I have developed a replacement of HP's smtp mail that includes an archive of all sent emails with the ability to easily resend mails without having to fiddle with eventout records ot the mailapplication's pointer.
See attach pdf for full description of the solution.