6 Years ago it was relatively easier to build and send out newsletters using shared hosting and a newsletter script like 12All or phplist. Slowly hosting companies started to place limits on the amount of emails you could send per minute and per day and that stopped that. Hosts then told us that you could a buy dedicated server instead and then send out as many emails as you like.
Again this worked for a few years until google, hotmail and yahoo started to blacklist ip addresses and the groups of ip addresses. Which meant that you would need to find another way to send out emails.
Services like mailchimp are great but if you manage more than 30,ooo emails then this whole service becomes very expensive.
Lately there has been a large increase in cost effective SMTP providers. Many of whom will give you an account for free with a small monthly and daily limit. They have become popular as mobile apps increasingly rely on then for email sending. We still use newsletter software to built and send emails but all our newsletter emails now go via mailjet using the Mailwizz php/mysql script.
The benefit of using an SMTP provider like mailjet, is that they use additional logic to decide whether to send the email delayed or even send it at all. If the email has recently failed for a different sender on their systems then your email send will be pre blocked. Additionally if you are sending 500 emails to a single domain then they will stagger the emails accordingly to reduce the chance of their ip group being clicked.
Your web server stays clear of getting in trouble as non of the emails are actually coming from it.
I thought I would do some research and put together a list of SMTP mail senders and there pricing plans.
MailGun (by Rackspace)