Hi Nabeel,

1. You can first configure a "Search Repository" activity to look for entries at a particular location. Make sure you also retrieve "Created By" from the "Additional Properties" window. Please see the attached document for further reference.
2. Next, create a token with multiple values allowed. You don't need to store any values at this point; just keep it blank.
3. Use the "For Each Entry" activity to process all the output entries retrieved by the search activity. Within the loop, you want to append the token created in step 2 so that it can store all of the "Created By" values for each entry

Please see the attached images for reference. 

Regards,

Comment: FYI, this approach is only suitable when you are working with smaller number of entries (i.e. less than a few hundred). This is because "For Each" loop is inefficient over large data sets. Furthermore, there is a size limit on the email message body so the email server may not be able to send the email itself. The solution proposed by Miruna would be the better choice especially in that type of scenario.