Report Tasks Outbound Manual Emails

We send out automated emails as part of marketing campaigns under a salesperson's username. During an email sequence, if a recipient responds then our salesperson using gmail integration responds manually to the potential customer. How can we count the number of emails sent by a salesforce user for a given period? 

I can create a report showing all tasks and filter by subject but the option to filter by HTML body is not offered. I was going to filter based on words the salesperson would write which are not part of the automated outbound emails. I tried filtering on status field contains "Sent" but that doesn't work - https://prnt.sc/23bvdh7. 

I checked the workaround (https://trailhead.salesforce.com/trailblazer-community/feed/0D54S00000A8yZ9SAJ)  for creating a report for sent emails from SF but my understanding is that is all sent emails, I don't want to include the automated emails. Thanks.