CF11standard Mail Spool Queue (delivery order)

I was wondering if anyone had insight to the processing order of the cfmail spool queue.  I was under the impression that it would be under first in first out, but as I am monitoring it today I am seeing that is not the case.

at 1:30pm I am seeing emails yet to go out from 8:45am, and I am watching other emails from later batches go out before them.  It almost appears like coldfusion is treating the emails like they are in batches, evenly plucking a message from every batch that comes in rather than attacking them in the order that they were received.

My customers tend to send their emails in batches of 1000-3000 emails at a time based on their queries.  Sometimes a single transactional message appears in that queue too.  Somtimes it goes out before the ones before it, or after.

Some days it can get pretty busy, but eventually it all catches up and the queue empties out.

Thanks

steve