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.
ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.
TrueMail.io - TrueMail.io is an email checker service.
clearout.io - Clearout Email Finder & Email Verification Service - Drive sustainable business growth by expanding your reach, lowering hard bounces, and improving deliverability rates.
Simple Email Verifier - Simple email verifier is PHP script use Trumail API to verify bulk email addresses.
NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.