Most Cost Effective Way To Send Email

In the long run I'd also say that setting up your own server is the most cost effective way. The only ongoing cost you have is for the server itself. It should be a vps or dedicated server, so no $3.99 hosting! but still cheaper than any autoresponder.

But it takes a lot of time and skill to warm up the ips and if you only have cold data it will be even more difficult.

Once you have started and segmented your data into openers and clickers - ie when you have warm data, warming up ips is much easier.

If you are just starting out I'd recommend you set up an account with mailrelay. You can send 15k mails free per month. If you use their platform you can only have 3k subs, but if you use mailwizz + the smtp relay from mailrelay you can have as many subs as you like.

Get a good shared hosting (ssd or cloud) and install mailwizz. For what you are going to do - getting your feet wet with email marketing - this is going to be enough.
You can also add a mailgun account to mailwizz - another 10k free email sends.
Elastic Email is also an option, the give you 150k free email sends, but they are also very strict and have closed down any accounts I know of who tried to do affiliate or cpa marketing with cold leads.

When you have installed mailwizz, you will see what sending servers you can add - smtp or api - there's a lot more, and some of them give free contingent. Try them.

I can also say that all of them closed me down except mailgun and mailrelay.

Using smtp relays like mailgun is very costly if you send out lots of emails. So once you exceed the free contingent you should really think about setting up your own server

Most places that offer Interspire and PowerMTA are total BS.

First off, they are using hacked versions of the software, so there is no support other than what they can provide.

Interspire is footprinted because it's been abused by these types of places. So I would assume you would need to hack the header and make it generic. Which I have no idea what that takes to do. Also, the program is PHP, so it's not built for speed.

Then most of the places completely over charge for IPs. Because novice mailers don't know better and they can get away with it.

I could go on and on.

You want to work with mail friendly IP providers (won't shut you down over complaints) and will supply you with IPs at a fair price and have a reasonable IP replacement policy.

While the minimum costs to get started are much much higher than using an ESP. Your cost per email sent will be rock bottom dirt cheap. The reason why it's more costly to get started is because to send volume you need to get IPs in quantity. However, there are some exceptions.

Plus you need a mailer and commercial mailers are not cheap and they are mainly leased month to month. Also, keep in mind that you need the data to support the operational costs and turn a profit. So that's an additional investment.

It all adds up quickly.