Hi,
When I add a post to my latest announcement forum, the emails are tried to be sent immediately and postfix overloads and crashes and moodle stops sending emails (after about 300-400 emails sent). Every time I have to go into CWP (Centos Web Panel I have) to restart Postfix. How can I limit the number of emails sent per hour and que the rest to be sent the following hours, so all will be finished without issues? 

If it is not possible to set a limit for the number of emails on moodle, what should I do on the server side to overcome the email sending issue I mentioned above.

Moreover, what number should should I set the "SMTP session Limit" to? Is 1 OK and what is the logic of it? Does it have anything to do with the crash of postfix? Shall I increase the number to overcome the issue? I don't really get what session limit means and what is it intended for?

In a nutshell, I am always having issues when sending bulk info mails to my users (around 13.000 now) through the latest announcements. I need the latest announcements forum to send the emails without issues, prefereably in a short time. I need some detailed information to guide me, and I will really appreciate that. Moreover, if possible, could you have a handy solution for it in the next update.

Thank you in advance.
Tumer

Details of my moodle and server:
Moodle version: 4.3 (just upgrade from 4.1 but I had the same issue in 3 and 4 as well)
Error messages: On server side, postfix failed message I reciev in my e-mail; then I restart postfix and PolicyD
Operating system: Centos7
Php Version: phP 8.0 ( I had the same problem in 7.4 as well; guess not related)
DB: Mariadb (Mysql earlier on 4.1)
I have set the PolicyD hourly limits to over 20.000 on server side through CWP, in case that might be the reason for Postfix crashing and not sending the rest of the emails.