[kh99]

I think you'd just want to increase "Number of emails to send per batch". I don't know what an appropriate value would be. The emails get sent by scheduled task, which runs when users load a page, so I suppose if you were to set that value too high, the script might time out before it sends them all. But maybe try setting it to 100. The task runs every 10 minutes, so that's 600 per hour or 14400 per day, so that might clear your queue by tomorrow.