Если вам нужно организовать отправку писем из своего .NET Core веб-приложения, MailKit вам поможет!
https://dotnetcoretutorials.com/2017/11/02/using-mailkit-send-receive-email-asp-net-core/
https://dotnetcoretutorials.com/2017/11/02/using-mailkit-send-receive-email-asp-net-core/
.NET Core Tutorials
Using MailKit To Send And Receive Email In ASP.NET Core - .NET Core Tutorials
Whether you're looking for an email library for your ASP.NET Core app or just want to know more about MailKit, this introductory guide is the perfect place to start.