So on second thought, i'm unsure if we're able to send mass-mail to the userbase. I've fixed the system in myBB, however our API we used to send the mail only allows a certain number of mail per month. (A number we won't reach normally) - However a blast to everyone on the forums, exceeds that limit instantly.
We need to pay money for more support. Our server costs are high enough currently, for something small like that, I don't really think it's worth buying.
The mass-mail idea is a great one. It might be outside our capacities for the time being though.