public class MailServer
{
    public string Host { get; set; }
    public int Port { get; set; }
    public bool UseSSL { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
    public string FromAddress { get; set; }
    public MailServer()
    {
    }
}

public void ConfigureServices(IServiceCollection services)
{
    // .....
    services.Configure<MailServer>(Configuration.GetSection("MailServer"));
    // .....
    services.AddSingleton<IScheduledTask, ScheduledTask>();
}

public interface IScheduledTask
{
    void MonitorCloudHosts();
}

public class ScheduledTask : IScheduledTask
{
    private readonly IServiceProvider _ServiceProvider;
    private readonly MailServer _mailServer;

    // note here you ask to the injector for IServiceProvider
    public ScheduledTask(IServiceProvider serviceProvider, IOptions<MailServer> optionsAccessor)
    {
        _ServiceProvider = serviceProvider;
        _mailServer = optionsAccessor.Value;
    }

    public void MonitorCloudHosts()
    {
        // Do some stuff
        var xyz = _mailServer.Host;
    }
}