My bad, I read this as “after analysing all the newsletters for the day” – implying that you receive multiple emails throughout the day, and only want to re-process the new rows inserted into the spreadsheet.
In that case, you should just aggregate after the Sheets module, perhaps a Text Aggregator would work to combine all of the inputs?
Hope this helps! Let me know if there are any further questions or issues.
— @samliew
P.S.: Did you know, the concepts of about 70% of questions asked on this forum are already covered in the Make Academy. Investing some effort into it will save you lots of time and frustration using Make later!