It looks like all of the emails are sent from: /notifications/send_enquiry_email.php
I'm not sure why we build up an array and create a recordset on this page at all since it appears we aren't actually using it. You can delete lines 544-572. Those lines are repeated on the page that actually sends the emails.
To see the emails that get sent, I'd probably write them to a log file.
I added code to do the logging. The code I added is on lines: 38, 95, and 134.
It should create a file named email_log.txt that will log all of the emails sent. Once you have debugged you should comment out line 134 so that log file doesn't keep growing.