I'm not sure what functionality you're looking for but I use the app Now Back in Stock to manage pre-orders (collecting emails for products not in stock).
Founder of Speed Boostr (Shopify optimization and dev agency). Creator of Theme Scientist (A/B testing app). Creator of Order Automator (app that auto tags + fulfills orders, send emails). Creator of Tip Jar (add a tip button to your store). Creator of Shopify Analyzer (free performance analysis tool). My team also builds custom apps and automated solutions. Enjoy the adventure!