Using Configure method to register the options

Startup.cs

// Startup.cs
public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        // Some code...

        services.Configure<MailFeature>(Configuration.GetSection(nameof(MailFeature)));

        // Some other code....
    }
}

// Inject dependency in controller.
// using Microsoft.Extensions.Options;
public class HomeController : Controller
{
    private readonly ILogger<HomeController> _logger;
    private readonly IOptions<MailFeature> mailFeatureOptions;

    // the Options class is directly injected
    public HomeController(ILogger<HomeController> logger, IOptions<MailFeature> mailFeatureOptions)
    {
        _logger = logger;
        this.mailFeatureOptions = mailFeatureOptions;
    }
}