diff --git a/src/SpamGuard/Program.cs b/src/SpamGuard/Program.cs
index 3751555..dd9eced 100644
--- a/src/SpamGuard/Program.cs
+++ b/src/SpamGuard/Program.cs
@@ -1,2 +1,78 @@
-// See https://aka.ms/new-console-template for more information
-Console.WriteLine("Hello, World!");
+// src/SpamGuard/Program.cs
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Serilog;
+using SpamGuard.Configuration;
+using SpamGuard.Services;
+using SpamGuard.State;
+using SpamGuard.Tray;
+
+namespace SpamGuard;
+
+static class Program
+{
+    [STAThread]
+    static void Main()
+    {
+        Application.EnableVisualStyles();
+        Application.SetCompatibleTextRenderingDefault(false);
+        Application.SetHighDpiMode(HighDpiMode.SystemAware);
+
+        var dataDir = Path.Combine(
+            Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),
+            "SpamGuard");
+        Directory.CreateDirectory(dataDir);
+
+        Log.Logger = new LoggerConfiguration()
+            .WriteTo.File(
+                Path.Combine(dataDir, "logs", "spamguard-.log"),
+                rollingInterval: RollingInterval.Day,
+                retainedFileCountLimit: 7)
+            .CreateLogger();
+
+        try
+        {
+            var host = Host.CreateDefaultBuilder()
+                .UseSerilog()
+                .ConfigureAppConfiguration((context, config) =>
+                {
+                    config.AddJsonFile("appsettings.json", optional: false);
+                    config.AddEnvironmentVariables("SPAMGUARD_");
+                })
+                .ConfigureServices((context, services) =>
+                {
+                    services.Configure<SpamGuardOptions>(
+                        context.Configuration.GetSection(SpamGuardOptions.SectionName));
+
+                    // State stores
+                    services.AddSingleton(new ProcessedUidStore(dataDir));
+                    services.AddSingleton(new TrustedSenderStore(dataDir));
+
+                    // Services
+                    services.AddSingleton<ActivityLog>();
+                    services.AddSingleton<ImapClientFactory>();
+                    services.AddSingleton<EmailClassifier>();
+                    services.AddHttpClient<EmailClassifier>();
+
+                    // Background services
+                    services.AddSingleton<InboxMonitorService>();
+                    services.AddHostedService(sp => sp.GetRequiredService<InboxMonitorService>());
+                    services.AddHostedService<TrustedSenderService>();
+                })
+                .Build();
+
+            host.Start();
+
+            Application.Run(new TrayApplicationContext(host));
+        }
+        catch (Exception ex)
+        {
+            Log.Fatal(ex, "Application failed to start");
+        }
+        finally
+        {
+            Log.CloseAndFlush();
+        }
+    }
+}
diff --git a/src/SpamGuard/SpamGuard.csproj b/src/SpamGuard/SpamGuard.csproj
index e221b19..e4797c3 100644
--- a/src/SpamGuard/SpamGuard.csproj
+++ b/src/SpamGuard/SpamGuard.csproj
@@ -12,6 +12,9 @@
     <PackageReference Include="MailKit" Version="4.*" />
     <PackageReference Include="Anthropic" Version="12.*" />
     <PackageReference Include="Microsoft.Extensions.Hosting" Version="8.*" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="8.*" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="8.*" />
+    <PackageReference Include="Microsoft.Extensions.Http" Version="8.*" />
     <PackageReference Include="Serilog.Extensions.Hosting" Version="8.*" />
     <PackageReference Include="Serilog.Sinks.File" Version="5.*" />
     <PackageReference Include="Serilog.Sinks.Console" Version="5.*" />