Doing uncommon things may have uncommon consequences.
First of all, the queue processing system is not meticulous on the second on managing the sending. Basically all it does is check every so often if there’s something to send and then invoke it up to the limits it is allowed, and then check back some other time.
Secondly, it is set up to send in “batches”. It’ll send X emails, wait a little while and then check if there’s more to do and do it.
If you want atomic precision, it’s not going to work. You could try to set up some local system that handles that.
The queue processing, both remote and local is simply about:
- I need my newsletter sent to X subscribers
- send a few, wait a while
- have all been sent, great, if not, go back to step 2
With the remote processing system, it rotates over everyone who is sending, so if there are other people sending at that time, the delay between 2 and 3 may vary.