My biggest problem was that I got confused between "Parameters" and "Variables". I'm still not sure if I understood it 100 percent, but I got it to work, and it works very well. Below screenshot shows the steps.
In a nutshell:
1) You need a transformation that creates the list through which you want to iterate. The last step is a "Job Executor". The Job Executor will run a job for each entry in the list. You need to define the values (= Variable/ Parameter) you want to pass to the subsequent jobs and transformations.
2) Then you need to define the job the job operator should run. In my case, this job contains two transformations, "Prepare File" and "Send Email". You don't need to define the parameters here again.
3) Then, in each transformation, use the "Get Variables" step. The "Get Variables" button likely won't show them, but you can just type them in manually. In my example, which each iteration I'm sending a different email address, which is stored in "Parameter_Email".
That's all, I was able to send about 200 emails in less than two minutes.
Just posting it here in case somebody else finds this helpful.
