I think you may want the confQUEUE_SORT_ORDER option. This prioritizes how the queue is processed, e.g. by time, host, etc.
If sending to hotmail be careful not to trigger their spam filters by sending too many messages at once.
Aslo, I think there is another command limit how many emails sendmail will submit per connection. Using this this with host based priority, multiple queue runners and an increased connection cache can drastically speed up delivery.
If you are looking for performance, consider moving to postfix. On Red Hat boxes it is also supported. Much easier to tune and configure than sendmail.