Apility.io - Threat Intelligence Anti Abuse API to find out in advance if your users will be good customers. Learn if your users are on an abuse blacklist and decide how to proceed.
ipinfo.io - Simple IP address information.
TrueMail.io - TrueMail.io is an email checker service.
ipdata.co - Get the Geolocation, Organisation, Currency, Timezone, Calling Code, Flag, Proxy, Tor and Threat intelligence data from any IPv4 or IPv6 address.
Simple Email Verifier - Simple email verifier is PHP script use Trumail API to verify bulk email addresses.
ifconfig.co - What is my IP address? — The best tool to find your own IP address, and information about it.