To create the filter Lets have two email ids. firstname.lastname@example.org and email@example.com.
1. Go to Gmail search option put their email like this
2. Click on create filter with this search and select the label you create like the one I have create in create in my case as My Users and also check apply filters to matching conversations as given below.
3. Once you will click on create filter, Every email coming from the user will be seen as My Users. and then you can recognize that you have received email for follow up.
Please comment if you are facing challenge in configuring Gmail filters.