Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.
Polymail - Native email app for email productivity.
CallApp - Free Caller ID & Call Blocker app that allows mobile users to block phone calls, identify calls, blacklist unwanted callers and much more.
Morning Mail - A new way to manage your mail. Tinder for email.
CallerSmart - CallerSmart is an application that is basically used for the purpose of looking up mystery phone numbers for free.
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.