Invite to webinars
Invite your visitors to webinars. Create an action path in such a way that you're going to target specifically: those with/without email addresses in the data base. Next, depending on their reaction, you will go on with a particular scenario of the path.
Let's start from Trigger: Event Trigger (here, the event means when a visitor clicks "join a webinar") and next Filters: Email → unknown . In this way, we send a message to only this particular group of our target audience. Insert Action: Show a form with a kind request to insert the email address; next Delay to wait 30 secs and check if a given person has already filled in a given form.
If yes, Condition: Form submitted?, then let's send an email campaign to this person with all the necessary information about the webinar (Action: Send a new email campaign). However, if a person doesn't submit the form, then Action: Send a chat message with a message: "Hi, are you sure you don't want to learn more about ...? Just submit your email address!". Connect this module with the Show form module that you have already created.
The second path will start from Filters: Email → any. Now, what you need to do is to connect this module with the Send a new email campaign module that you've already inserted.