Maintaining a Healthy Marketing Database

Thanks @Sanford Whiteman​! I will read the product doc again for better understating. 

If any lead will update their his/her email address then new lead will be created.

Why would you think so?  An update is just that, an update, and it can come in via many channels.

A form post with a new email address will create a new lead, but that's not the only way for data values to be changed.

In any case please open a new thread in Products​ as this isn't the best place for tech questions.

I have a question here on manage invalid emails. If any lead will update their his/her email address then new lead will be created. By default it is not marked as invalid the why we need this step?

In the "Unsupress Marketing" campaign example, it doesn't actually handle "Closed/Won" OR "Closed/Lost" as the "Closed/Lost" criteria isn't set.