Top 20 NuGet anti-spam Packages

A simple, no-drama, reCAPTCHA validation library that works with ASP.NET Core, Razor Pages, MVC 5, and WebForms.
The GoogleRecaptchaMvc is a .NET library used to create the html control of Google Recaptcha for asp.net mvc.
The GoogleRecaptchaWebForms is a .NET library used to create the server control of Google Recaptcha for asp.net web forms.
The GoogleRecaptcha is a .NET library used to integrate the Google Captcha into the web applications based upon the asp.net platform.
Encapsulates Google ReCaptcha functionality for ASP.Net MVC
MailSystem is a suite of .NET components that provide users with an extensive set of email tools. MailSystem provides full support for SMTP, POP3, IMAP4, NNTP, MIME, S/MIME, OpenPGP, DNS, vCard, vCalendar, Anti-Spam (Bayesian , RBL, DomainKeys), Queueing, Mail Merge and WhoIs