How to merge Email sent from Zendesk

Hi everyone,

I was wondering if there's a chance (or an app) to merge similar emails sent from zendesk into one single thread.

Let me expand: 

We are testing a specific approval procedure which requires an email sent to an external approver. 

Since the approval requests toward the same approver are multiple, it could come in handy to have a merging system to have just one thread so the approver can open one occurrence.

Anybody has tips regarding this matter?

Many thanks in advance

Regards

Leonardo Lenk