An autoresponder is most essential for email marketing. It allows you to schedule and automate your emails and easily create different email lists.
Emails collected are saved and organized under the appropriate list names.
This means if you have 3 different subscription forms, a newsletter subscription form, a free ebook subscription form and a free training subscription form in your autoresponder you will be able to see who on your list signed up through your newsletter form, from who signed up through your free book and free training subscription.
In an autoresponder, you can track your email open rate. This means, emails that are sent out to your subscribers, you can view in your autoresponder, the subscribers that open your email from the ones that don’t.

You can also track links – track when the links in your email are open.
As an email marketer, it is required to provide a simple way for your subscribers to unsubscribe if they choose to do so. Autoresponder also provides this facility.
Choosing An Autoresponder
There are several autoresponder services available.
To use one of the available Autoresponder services, all you really need is a domain name.
Once you have a domain name you can create landing pages under your domain name which acts as your website.
And certainly, if you want to design a full website with pages and tabs it can be done in some Autoresponders, it might be a bit technical but doable.
The problem I find with these Autoresponder services is that they are pricey and most time very complicated.
You are charged on a subscription basis, meaning, you have a monthly recurring bill. Your recurring bill increase as your email list grows.