Hi,
Let's do some math. ;-)
You have configured your automatic sending proces to send two batsches of 80 emails every 2 minutes. That would result in 4.800 e-mails per hour. The math: Two batsches per hour every two minutes results in 60 batsches per hour, Multiplied with 80 emails per batch equal;s 4.800 emails per hour.
And yet, you don't achive this sending speed. Here's why:
When you activate the automatisc sending our cron servser is calling your cron url to activate the automatisc sending process. The minimum time interval is 15 minutes and results in sending one batch every time the cron is triggered.. So even if you set the cron interval to two minutes, the cron only gets activated every 15 minutes.
When your cron task is triggered every 15 minutes and you send a batch of 80 emails you will send 320 emails per hour.
Now, when you configure an interval shorter then 15 minutes and/or more then one batch you will make use of something which is calles web cron. In this case your cron task will be triggered by your website visitors. This will word fine if you have lot's of visitors. But if your website is not visited frequently enough the web cron is not triggered often enough. So it will work, but you cant't do your math because it completely depends on the number of visitors.