Program using and Event for Source: can we add Sender (CSM) fields via lookup?

We are testing a Program where the source is an Event (api payload).  Part of the data passed in the event is the SFDC Account ID for each recipient.  I was given the impression that I’d be able to fetch and use values for other Standard Fields (Sender Name, Sender Email Address, etc) by looking up those values on the CSM via the Account ID.  However, I can’t seem to do so. 

Am I missing something?  We are hoping to keep the Event’s payload as lean and efficient as possible, but right now the only way I see to set the CSM’s email address as the “Sender Email Address” will be to have our dev add those values to the Event.