Veeeery slooooowly...

For free, it would take a long time, I'd imagine. Almost every email service out there has hourly and daily limits on how many emails you can send. You might have to find a paid service to do this, in which case I apologize but I haven't researched those. I was looking for a free service because that's about what my group can afford for this reunion, and we'll only have a maximum of 400-500 emails we need to send out at a time.