[gbaygon]

...we need the email to inform about the current progress and select future beta users.

So why don't you hint about it in the landing page?

My process was:

  1. Open the page
  2. Saw "build your own webinar tool"
  3. Saw email field
  4. Saw join button

and thought: "If I enter my email in this box this will give me access to some kind of personalizable webinar tool, but I don't know if I need this yet", then closed the page.

You need to rework the landing page so the visitor knows what they are doing exactly when they click the "JOIN NOW!" button.