How to check if one email is 100% contained in another?

Question

How can you delete emails that are 100% embodied in another email efficiently? I want to avoid reading each email individually to check manually. I use MS Outlook 2013.

For example, let's say that in January, I email X. In February, X replies. In March, I email X back the 2nd time. In April, X replies the 2nd time.

The efficient method desired should ignore and leave alone emails which aren't perfect subsets of others (eg if in X's April email, he changed his Feb response, then X's should be kept.)
For example, in what follows, assume that X includes all prior correspondence in his emails.

1. The method should delete the Feb. reply, because the April reply comprises it.

2. How can the method delete my two sent emails in my Sent Email folder, because X's April reply will comprise them?

Update: I thank and acknowledge user thims's comment below, but how can the above be achieved the above for specific emails only (and NOT to the entire folder)?