There is a reason why email service providers such as Getresponse, Aweber etc have 10s of employees who are specialists in email delivery.
Delivery of thousands or in some cases millions of emails over a short period of time requires infrastructure and technology – you have a news item you want it delivered now, not in 6 hours when their servers get around to it, and you want a cooperative partner handling any spam complaints, not a company prone to hit the permanent off button without recourse.