Sending half a million emails takes too long: 6 to 8 hours. Quota allows 90 emails per second. Sending from a dedicated server with nice performance, so memory/connection should not be the issue. Using batches of 50 emails at once.
Tryed varying number of emais in a batch: more than 50 causes CURL errors: seems like there's no response from Amazon to some of the threads. Even with 50 in a batch and a 1200ms pause between batches each mailout gets several hiccups.
So an average batch of 50 take from 4 to 6 s to complete + 1.2s pause — quite a long for 500k daily mailout.
Please advice how to tune the mailing to get its speed closer to the 90 mails/s.