So I figured this out by creating new variable and assigning to it value of the Exchange list.
In pseudocode something like this:
new_var = %RetrievedEmails[0]%
Then I was able to get to the properties of the new_var list a figure out the correct syntax, which is %RetrievedEmails[0]['From']%. I have no idea, why this particular property has to be written in that format, and not like the other properties, for example %RetrievedEmails[0].Date%.
There is some serious magic behind the curtains.