How to increase the speed of sending emails with VDS?

Question

linux

Good day friends comrades!
I have been struggling with the problem of mailing letters for several months now. 70k letters do not go away in two hours, even if you crack.
Available: VDS CPU 4 Core and 8Gb RAM
Vesta CP is installed on it, respectively, PHP5, APACHE2 + NGINX comes out of the box, Exim4 is used for mailing. phpList
is used for mailing.
And the database is slightly more than 76k emails.
According to the customer, there was a time when the entire mailing was sold out in 2 hours. This happened to me too, but not more than a day or two, and then again a blockage in the Exim mail queue and a drop in the mailing speed.
phpList shows a mailing rate of 10k/letters per hour.
upd:
everything you need to avoid getting into spam is set up.
upd2:
The mailing is not spam, but information from the site, to which users themselves have subscribed. There is a link in the email where they can unsubscribe. Everything is done according to the rules of mail.ru.

Answer 1

I assume that the problem may be due to unresponsive or slow responding servers. Cut timeouts, number of retries, and frequency of retry attempts.

Answer 2

Try increasing the number of Exim workers and the number of parallel sends:

queue_run_max = 10
remote_max_parallel = 10

Values ​​are for example only, you can choose your own...