Some members on LinkedIn set restrictions that require you to have their email already in order to send them an invitation.
With this feature enabled, Growth-X will discover the email and you will be able to send the invite. You'll also be able to export such emails from the Prospects tab.
In order to enable it you must first purchase data credits. To do so just send an email to help@growth-x.com stating the number of credits you'd like to purchase. Pricing packages are available here.
How to activate the feature:
Go to the 'Campaign' tab in the app, create a new campaign or select a previous one.
Scroll to the bottom of the campaign template and toggle the option 'Invite people who require email using data credits'
Hit 'require email using data credits' and save.