Hi Ricardo,
This can only be done by using 3rd party mass email tool. I know a very good tool for this purpose which can remove this limitations and can deliver unlimited emails. Salesforce had 1000 emails per day limitations. If we are looking for less than 1000 emails per day , let me know I will code for this. Else we have to get the 3rd party solution.
Based on the cost of the solution we can update the bid pricing accordingly. Want to implement this without much cost involved.
Thanks,
Amit