well you can manually adjust how often the queue sends and how many it sends per batch.
So if you have 1500...say you need to save like 250/hr for other emails your board sends out, so this means you can send 1250/hr without going over your limit.
If you wanted large batches you could send only like 250 every 15min or do small batches of 20 every 3min. Just as an example...I didn't actually figure the math out on those