How to link registration on the site to the mailing service?

Question

API

Hi people. You need something like this:
1. Have your own mailing list (GetResponse / Smartresponder) - you haven't chosen a service yet
2. Have a website
Is it possible to make it so that when registering on the site, the user is automatically entered into the mailing list of one of these services?
Tell me, please, in which direction to dig. Or where to read something on this topic.

Answer 1

For example, you can read the documentation for the desired interface. For example, here: apidocs.getresponse.com/en