I would note that I have no server restrictions for email sending and according to the documentation:
A special URL is called by our server every 15 minutes to handle automated tasks, but it's also triggered on every page loaded on your website if you decide to send every 5 minutes or send multiple batches at once for example. If you set to send emails every 5 minutes you'll need users to visit your website every 5 minutes.
However, that can't be working right because my site has way more than 1 visitor every 5 minutes, yet the send process take 5+ hours to send around 2,000 emails.
Please advise how to fix this issue.