Bulk email service

Hi there,
I transferred an amateur forum to a new hosting service but I found out later that one of the administrators of this forum had been using a mail ring to contact the users. The problem now is that the present server will not allow so many mails, just over 2000, to be sent at the same time, but only about 100 mails per hour. I would like to know if you have any idea how we can overcome this problem, maybe with a plugin phpbb or some free user friendly programmes so that he can carry on communicating with his clients without the server crashing. I suppose that something can be done with the code but I really wanted to know if there already is a solution for this kind of problem as this kind of forum is quite popular and considering the fact that the service provider is one of the most important I know.
Thank you