When an email is sent to the related contact, the Update Client Details app creates a task that is also added to the activity history of the account, as shown in the image below.

In Lightning - 

In Classic -

Additionally, there are the managed fields of the Update Client Details app on the Account object, which get updated when an email is sent to the account, as shown below- 

This helps you to keep track of when the account has received the form previously and by which e-mail. You can add these fields into your account layout for better understanding.