OOPSpam Anti-Spam API is a powerful anti-spam filter for contact forms, comment systems, live chat- the limit is your creativity!
OOPSpam Anti-Spam API's advantages over alternatives:
We also have a WordPress plugin, get it here: OOPSpam Anti-Spam – WordPress plugin | WordPress.org
Mailgun - A set of powerful APIs that enable you to send, receive and track email from your app effortlessly whether you use Python, Ruby, PHP, C#, Node.js or Java.
Akismet - Akismet is a spam fighting service that protects millions of WordPress sites from comment and contact form spam.
Mandrill - Mandrill is a new way for apps to send transactional email. It runs on the delivery infrastructure that powers MailChimp.
CleanTalk - Spam protection for WordPress, Joomla, Drupal, and any other websites
PHPMailer - Email sending library for PHP.
hCaptcha - Do you use a captcha to keep out bots? hCaptcha is a drop-in replacement for reCAPTCHA that earns website owners money and helps companies get their data labeled.