look at this post
https://forum.mailwizz.com/threads/...send-1-000-000-mails-at-24-hour.198/#post-867 regarding cron settings as well. Personally I wouldn't disable some of the settings and allow a pause, it can be a couple of seconds.
I would also check to see how long it takes to open the SMTP connection.
If you are confident that you have tuned PHP correctly and MySQL and that you aren't hitting any limits with CPU/MEmory/Virtual Memory then you have to look at the connection to the SMTP server as many people are sending thousands of emails per hour with MW.
Some tips on MySQL (if run on separate server) tuning:
innodb_buffer_pool_size: Setting this to 70-80% of memory (server's RAM) is a safe bet. E.g. 12G on a server with 16GB of ram. You may want more if your running a dedicated server with mostly InnoDB.
*innodb_log_file_size: This depends on your recovery speed needs, but 256M seems to be a good balance between reasonable recovery time and good performance
*
Note: If you modify innodb_log_file_size without removing the existing logs, MySQL will fail to restart and InnoDB will complain about the size of the changed log file.
This is the proper way to increase innodb_log_file_size:
- shutdown mysql server
- make backup of data and log files
- remove InnoDB log files
- set new value for innodb_log_file_size in my.cnf
- start mysqld
- check error logs to ensure everything went fine.
innodb_log_buffer_size: 4M is good for most cases
innodb_lock_wait_timeout: 300 (this is seconds) is good for most cases