The Mailgun C# SDK by Mailgun communicates to the API to integrate email features into applications. Useful to validate and analyze user interactivity. Includes RestSharp, a REST and HTTP client for .NET. It also offers Mono, a cross-platform framework sponsored by Xamarin.
SendGrid announced its latest endpoint for its Web API: v3/mail/send. The endpoint rounds out the v3 release that began last year. With the new send endpoint, SendGrid has realized its goal of complete API management via API. All of the v2 functionality remains available with additional features.