feat(notifications): EWS branch in the email delivery adapter

src/ZB.MOM.WW.ScadaBridge.NotificationOutbox/Delivery/EmailNotificationDeliveryAdapter.cs

@@ -4,6 +4,7 @@ using ZB.MOM.WW.ScadaBridge.Commons.Entities.Notifications;
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
 using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
 using ZB.MOM.WW.ScadaBridge.NotificationService;
+using ZB.MOM.WW.ScadaBridge.NotificationService.Ews;
 
 namespace ZB.MOM.WW.ScadaBridge.NotificationOutbox.Delivery;
 
@@ -18,6 +19,14 @@ namespace ZB.MOM.WW.ScadaBridge.NotificationOutbox.Delivery;
 /// Transient) — the canonical central-side email delivery path. The prior
 /// site-shaped <c>NotificationDeliveryService</c> was deleted with sites no longer
 /// delivering notifications.
+/// <para>
+/// The configured <c>SmtpConfiguration.Transport</c> selects the submission mechanism:
+/// <c>Smtp</c> (the default for every row that stores no transport) takes the SMTP path
+/// above; <c>Ews</c> hands the message to <see cref="IEwsMailSender"/> instead — one
+/// <c>CreateItem</c> SOAP call to an on-prem Exchange endpoint. List resolution, recipient
+/// resolution, configuration selection and address validation are shared by both
+/// transports; only TLS mode is SMTP-specific.
+/// </para>
 /// </summary>
 public sealed class EmailNotificationDeliveryAdapter : INotificationDeliveryAdapter
 {
@@ -26,6 +35,7 @@ public sealed class EmailNotificationDeliveryAdapter : INotificationDeliveryAdap
     private readonly OAuth2TokenService? _tokenService;
     private readonly ILogger<EmailNotificationDeliveryAdapter> _logger;
     private readonly NotificationOptions _options;
+    private readonly IEwsMailSender? _ewsMailSender;
 
     /// <summary>Initializes a new instance of <see cref="EmailNotificationDeliveryAdapter"/>.</summary>
     /// <param name="repository">Repository for resolving notification list recipients.</param>
@@ -33,12 +43,18 @@ public sealed class EmailNotificationDeliveryAdapter : INotificationDeliveryAdap
     /// <param name="logger">Logger instance.</param>
     /// <param name="tokenService">Optional OAuth2 token service for Microsoft 365 Client Credentials auth.</param>
     /// <param name="options">Optional notification options providing documented fallback values.</param>
+    /// <param name="ewsMailSender">
+    /// Optional EWS mail sender used when the selected configuration row sets the Ews transport.
+    /// Registered by <c>AddNotificationService()</c>; a host that omits that call leaves it null,
+    /// in which case an Ews row fails permanently rather than silently falling back to SMTP.
+    /// </param>
     public EmailNotificationDeliveryAdapter(
         INotificationRepository repository,
         Func<ISmtpClientWrapper> smtpClientFactory,
         ILogger<EmailNotificationDeliveryAdapter> logger,
         OAuth2TokenService? tokenService = null,
-        IOptions<NotificationOptions>? options = null)
+        IOptions<NotificationOptions>? options = null,
+        IEwsMailSender? ewsMailSender = null)
     {
         _repository = repository;
         _smtpClientFactory = smtpClientFactory;
@@ -47,6 +63,7 @@ public sealed class EmailNotificationDeliveryAdapter : INotificationDeliveryAdap
         // NotificationOptions supplies the documented fallback values used when a
         // deployed SmtpConfiguration row leaves a field unset (non-positive).
         _options = options?.Value ?? new NotificationOptions();
+        _ewsMailSender = ewsMailSender;
     }
 
     /// <inheritdoc />
@@ -89,9 +106,29 @@ public sealed class EmailNotificationDeliveryAdapter : INotificationDeliveryAdap
                 smtpConfig.Id);
         }
 
+        // An unknown transport is a configuration error that retrying cannot fix.
+        EmailTransport transport;
+        try
+        {
+            transport = EmailTransportParser.Parse(smtpConfig.Transport);
+        }
+        catch (ArgumentException ex)
+        {
+            _logger.LogError(
+                "Email notification to list '{List}' has an invalid transport: {Reason}",
+                notification.ListName, ex.Message);
+            return DeliveryOutcome.Permanent(ex.Message);
+        }
+
+        // TLS applies to the SMTP transport only — an EWS row's Port/TlsMode are unused.
+        // Parsed here, ahead of address validation, so the SMTP path's check order (and
+        // hence which reason surfaces for a row that is invalid in more than one way) is
+        // exactly what it was before the transport branch existed.
+        var tlsMode = SmtpTlsMode.None;
+        if (transport == EmailTransport.Smtp)
+        {
             // An unknown TLS mode is a configuration error that retrying cannot fix —
             // surface it as a permanent failure (SMTP TLS validation policy).
-        SmtpTlsMode tlsMode;
             try
             {
                 tlsMode = SmtpTlsModeParser.Parse(smtpConfig.TlsMode);
@@ -103,6 +140,7 @@ public sealed class EmailNotificationDeliveryAdapter : INotificationDeliveryAdap
                     notification.ListName, ex.Message);
                 return DeliveryOutcome.Permanent(ex.Message);
             }
+        }
 
         // A malformed sender or recipient address cannot be fixed by retrying —
         // surface it as a permanent failure.
@@ -121,6 +159,13 @@ public sealed class EmailNotificationDeliveryAdapter : INotificationDeliveryAdap
             .Select(r => r.EmailAddress!)
             .ToList();
 
+        // Everything above is transport-agnostic; the EWS branch takes over here.
+        if (transport == EmailTransport.Ews)
+        {
+            return await DeliverViaEwsAsync(
+                smtpConfig, recipientAddresses, notification, cancellationToken);
+        }
+
         try
         {
             await SendAsync(smtpConfig, tlsMode, recipientAddresses,
@@ -165,6 +210,115 @@ public sealed class EmailNotificationDeliveryAdapter : INotificationDeliveryAdap
         }
     }
 
+    /// <summary>
+    /// Delivers the plain-text BCC email through Exchange Web Services.
+    /// <para>
+    /// Every EWS-specific configuration defect (a non-HTTPS or relative endpoint, a non-Basic
+    /// auth type, a credential that is not <c>username:password</c>, or a missing sender
+    /// registration) is a permanent failure decided before the sender is touched — retrying
+    /// cannot fix a misconfigured row, and no half-formed request should reach Exchange.
+    /// </para>
+    /// </summary>
+    private async Task<DeliveryOutcome> DeliverViaEwsAsync(
+        SmtpConfiguration config,
+        IReadOnlyList<string> recipientAddresses,
+        Notification notification,
+        CancellationToken cancellationToken)
+    {
+        if (!Uri.TryCreate(config.Host, UriKind.Absolute, out var endpoint)
+            || endpoint.Scheme != Uri.UriSchemeHttps)
+        {
+            return PermanentConfigError(
+                "EWS transport requires an absolute https:// endpoint URL in Host; "
+                + $"got '{config.Host}'");
+        }
+
+        // Basic is the only credential shape the sender builds an Authorization header for;
+        // OAuth2/NTLM are documented follow-ons, not silent fallbacks.
+        if (!config.AuthType.Equals("basic", StringComparison.OrdinalIgnoreCase))
+        {
+            return PermanentConfigError(
+                $"EWS transport supports only Basic authentication; got '{config.AuthType}'.");
+        }
+
+        // Split on the FIRST colon only: a domain-qualified user name has none, but a
+        // password legitimately may contain one.
+        var parts = config.Credentials?.Split(':', 2) ?? [];
+        if (parts.Length != 2 || parts[0].Length == 0 || parts[1].Length == 0)
+        {
+            return PermanentConfigError("EWS credentials must be in 'username:password' form.");
+        }
+
+        if (_ewsMailSender == null)
+        {
+            return PermanentConfigError(
+                "EWS transport configured but no EWS sender is registered");
+        }
+
+        var timeoutSeconds = config.ConnectionTimeoutSeconds > 0
+            ? config.ConnectionTimeoutSeconds
+            : _options.ConnectionTimeoutSeconds;
+        var request = new EwsSendRequest(
+            endpoint,
+            parts[0],
+            parts[1],
+            config.FromAddress,
+            recipientAddresses,
+            notification.Subject,
+            notification.Body,
+            timeoutSeconds);
+
+        try
+        {
+            await _ewsMailSender.SendAsync(request, cancellationToken);
+
+            return DeliveryOutcome.Success(string.Join(", ", recipientAddresses));
+        }
+        catch (EwsPermanentException ex)
+        {
+            // Auth, wrong URL, schema fault or recipient rejection — not retried.
+            var detail = CredentialRedactor.Scrub(ex.Message, config.Credentials);
+            _logger.LogError(
+                "Permanent EWS failure delivering email to list '{List}': {Detail}",
+                notification.ListName, detail);
+            return DeliveryOutcome.Permanent(detail);
+        }
+        catch (EwsTransientException ex)
+        {
+            // Availability-shaped failure (network/timeout/5xx/server-busy) — retried.
+            var detail = CredentialRedactor.Scrub(ex.Message, config.Credentials);
+            _logger.LogWarning(
+                "Transient EWS failure delivering email to list '{List}': {Detail}",
+                notification.ListName, detail);
+            return DeliveryOutcome.Transient(detail);
+        }
+        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
+        {
+            // A caller-requested cancellation propagates; it is neither a success
+            // nor a delivery failure.
+            throw;
+        }
+        catch (Exception ex)
+        {
+            // Anything the sender did not classify is treated as permanent, mirroring the
+            // SMTP path's default-to-permanent stance.
+            var detail = CredentialRedactor.Scrub(ex.Message, config.Credentials);
+            _logger.LogError(
+                "Unclassified failure delivering email via EWS to list '{List}' ({ExceptionType}): {Detail}",
+                notification.ListName, ex.GetType().Name, detail);
+            return DeliveryOutcome.Permanent($"Email delivery failed: {detail}");
+        }
+
+        // Local helper: one log-and-park shape for every EWS configuration defect.
+        DeliveryOutcome PermanentConfigError(string reason)
+        {
+            _logger.LogError(
+                "Email notification to list '{List}' has an invalid EWS configuration: {Reason}",
+                notification.ListName, reason);
+            return DeliveryOutcome.Permanent(reason);
+        }
+    }
+
     /// <summary>
     /// Delivers the plain-text BCC email via SMTP. A permanent failure surfaces as
     /// <see cref="SmtpPermanentException"/>; transient failures propagate for the

src/ZB.MOM.WW.ScadaBridge.NotificationOutbox/ServiceCollectionExtensions.cs

@@ -26,10 +26,14 @@ public static class ServiceCollectionExtensions
     /// This extension covers only the outbox-specific registrations. The
     /// <see cref="EmailNotificationDeliveryAdapter"/> reuses the
     /// <see cref="ZB.MOM.WW.ScadaBridge.NotificationService"/> SMTP machinery —
-    /// <c>Func&lt;ISmtpClientWrapper&gt;</c>, <c>OAuth2TokenService</c> and
-    /// <c>NotificationOptions</c> — so the caller (the Host on the central node) must also
-    /// call <c>AddNotificationService()</c>. Re-registering those services here would
-    /// duplicate them; relying on <c>AddNotificationService</c> keeps a single source of truth.
+    /// <c>Func&lt;ISmtpClientWrapper&gt;</c>, <c>OAuth2TokenService</c>,
+    /// <c>NotificationOptions</c> and — for configuration rows selecting the EWS transport —
+    /// <c>IEwsMailSender</c> with its named HTTP client — so the caller (the Host on the
+    /// central node) must also call <c>AddNotificationService()</c>. Re-registering those
+    /// services here would duplicate them; relying on <c>AddNotificationService</c> keeps a
+    /// single source of truth. Each is an optional constructor parameter on the adapter, so a
+    /// host that skips <c>AddNotificationService()</c> still constructs — an EWS row then
+    /// fails permanently ("no EWS sender is registered") rather than falling back to SMTP.
     ///
     /// <see cref="EmailNotificationDeliveryAdapter"/> is registered <em>scoped</em> because it
     /// takes a scoped <see cref="ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories.INotificationRepository"/>

tests/ZB.MOM.WW.ScadaBridge.NotificationOutbox.Tests/Delivery/EmailNotificationDeliveryAdapterEwsTests.cs

@@ -0,0 +1,315 @@
+using Microsoft.Extensions.Logging.Abstractions;
+using NSubstitute;
+using NSubstitute.ExceptionExtensions;
+using ZB.MOM.WW.ScadaBridge.Commons.Entities.Notifications;
+using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
+using ZB.MOM.WW.ScadaBridge.NotificationOutbox.Delivery;
+using ZB.MOM.WW.ScadaBridge.NotificationService;
+using ZB.MOM.WW.ScadaBridge.NotificationService.Ews;
+
+namespace ZB.MOM.WW.ScadaBridge.NotificationOutbox.Tests.Delivery;
+
+/// <summary>
+/// Task 5: Tests for the EWS transport branch of the Email outbox delivery adapter —
+/// the transport parse, the EWS config-shape validation (each failure permanent and
+/// short-circuiting before the sender is touched), the request the sender receives,
+/// the typed transient/permanent outcome mapping, and the proof that an unset or
+/// "Smtp" transport still takes the untouched SMTP path.
+/// </summary>
+public class EmailNotificationDeliveryAdapterEwsTests
+{
+    private const string Endpoint = "https://ews.example.test/ews/exchange.asmx";
+
+    private readonly INotificationRepository _repository = Substitute.For<INotificationRepository>();
+    private readonly ISmtpClientWrapper _smtpClient = Substitute.For<ISmtpClientWrapper>();
+    private readonly IEwsMailSender _ewsSender = Substitute.For<IEwsMailSender>();
+
+    private EmailNotificationDeliveryAdapter CreateAdapter(bool withEwsSender = true)
+    {
+        return new EmailNotificationDeliveryAdapter(
+            _repository,
+            () => _smtpClient,
+            NullLogger<EmailNotificationDeliveryAdapter>.Instance,
+            tokenService: null,
+            options: null,
+            ewsMailSender: withEwsSender ? _ewsSender : null);
+    }
+
+    private static Notification MakeNotification(string listName = "ops-team")
+    {
+        return new Notification(
+            Guid.NewGuid().ToString(),
+            NotificationType.Email,
+            listName,
+            "Subject",
+            "Body",
+            "site-1");
+    }
+
+    /// <summary>
+    /// Wires a resolvable list with two recipients plus a single configuration row shaped
+    /// by the caller — the one knob every case below turns.
+    /// </summary>
+    private void SetupWithConfig(SmtpConfiguration config)
+    {
+        var list = new NotificationList("ops-team") { Id = 1 };
+        var recipients = new List<NotificationRecipient>
+        {
+            new("Alice", "alice@example.com") { Id = 1, NotificationListId = 1 },
+            new("Bob", "bob@example.com") { Id = 2, NotificationListId = 1 }
+        };
+
+        _repository.GetListByNameAsync("ops-team").Returns(list);
+        _repository.GetRecipientsByListIdAsync(1).Returns(recipients);
+        _repository.GetAllSmtpConfigurationsAsync().Returns(new List<SmtpConfiguration> { config });
+    }
+
+    private static SmtpConfiguration EwsConfig(
+        string host = Endpoint,
+        string authType = "basic",
+        string? credentials = @"dom\svc:pw",
+        string transport = "Ews")
+    {
+        return new SmtpConfiguration(host, authType, "noreply@example.com")
+        {
+            Id = 1,
+            Transport = transport,
+            Credentials = credentials,
+            ConnectionTimeoutSeconds = 45
+        };
+    }
+
+    private static SmtpConfiguration SmtpConfig(string? transport)
+    {
+        return new SmtpConfiguration("smtp.example.com", "basic", "noreply@example.com")
+        {
+            Id = 1, Port = 587, Credentials = "user:pass", TlsMode = "starttls", Transport = transport
+        };
+    }
+
+    private EwsSendRequest CapturedRequest()
+    {
+        var call = _ewsSender.ReceivedCalls().Single();
+        return (EwsSendRequest)call.GetArguments()[0]!;
+    }
+
+    private async Task AssertSenderUntouched()
+    {
+        await _ewsSender.DidNotReceive().SendAsync(
+            Arg.Any<EwsSendRequest>(), Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task Deliver_EwsTransport_SendsThroughEwsSenderAndReturnsSuccess()
+    {
+        SetupWithConfig(EwsConfig());
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        var request = CapturedRequest();
+        Assert.Equal(new Uri(Endpoint), request.Endpoint);
+        Assert.Equal(@"dom\svc", request.Username);
+        Assert.Equal("pw", request.Password);
+        Assert.Equal("noreply@example.com", request.FromAddress);
+        Assert.Equal(new[] { "alice@example.com", "bob@example.com" }, request.BccRecipients);
+        Assert.Equal("Subject", request.Subject);
+        Assert.Equal("Body", request.Body);
+        Assert.Equal(45, request.TimeoutSeconds);
+
+        Assert.Equal(DeliveryResult.Success, outcome.Result);
+        Assert.Contains("alice@example.com", outcome.ResolvedTargets);
+        Assert.Contains("bob@example.com", outcome.ResolvedTargets);
+        Assert.Null(outcome.Error);
+
+        // The EWS branch must never open an SMTP connection.
+        await _smtpClient.DidNotReceive().ConnectAsync(
+            Arg.Any<string>(), Arg.Any<int>(), Arg.Any<SmtpTlsMode>(),
+            Arg.Any<int>(), Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task Deliver_PasswordContainsColon_SplitsOnFirstColonOnly()
+    {
+        SetupWithConfig(EwsConfig(credentials: @"dom\svc:p:w"));
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        var request = CapturedRequest();
+        Assert.Equal(@"dom\svc", request.Username);
+        Assert.Equal("p:w", request.Password);
+        Assert.Equal(DeliveryResult.Success, outcome.Result);
+    }
+
+    [Fact]
+    public async Task Deliver_EwsTransientException_ReturnsTransient()
+    {
+        SetupWithConfig(EwsConfig());
+        _ewsSender.SendAsync(Arg.Any<EwsSendRequest>(), Arg.Any<CancellationToken>())
+            .ThrowsAsync(new EwsTransientException("503 server busy"));
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        Assert.Equal(DeliveryResult.TransientFailure, outcome.Result);
+        Assert.Contains("server busy", outcome.Error);
+    }
+
+    [Fact]
+    public async Task Deliver_EwsPermanentException_ReturnsPermanent()
+    {
+        SetupWithConfig(EwsConfig());
+        _ewsSender.SendAsync(Arg.Any<EwsSendRequest>(), Arg.Any<CancellationToken>())
+            .ThrowsAsync(new EwsPermanentException("401 unauthorized"));
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        Assert.Equal(DeliveryResult.PermanentFailure, outcome.Result);
+        Assert.Contains("unauthorized", outcome.Error);
+    }
+
+    [Fact]
+    public async Task Deliver_UnclassifiedSenderException_ReturnsPermanentAndRedactsCredential()
+    {
+        SetupWithConfig(EwsConfig(credentials: @"dom\svc:super-secret-password"));
+        _ewsSender.SendAsync(Arg.Any<EwsSendRequest>(), Arg.Any<CancellationToken>())
+            .ThrowsAsync(new InvalidOperationException(
+                @"boom for dom\svc:super-secret-password"));
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        Assert.Equal(DeliveryResult.PermanentFailure, outcome.Result);
+        Assert.DoesNotContain("super-secret-password", outcome.Error);
+    }
+
+    [Fact]
+    public async Task Deliver_CancelledToken_ThrowsOperationCanceledException()
+    {
+        using var cts = new CancellationTokenSource();
+        cts.Cancel();
+
+        var list = new NotificationList("ops-team") { Id = 1 };
+        _repository.GetListByNameAsync("ops-team", Arg.Any<CancellationToken>()).Returns(list);
+        _repository.GetRecipientsByListIdAsync(1, Arg.Any<CancellationToken>())
+            .Returns(new List<NotificationRecipient>
+            {
+                new("Alice", "alice@example.com") { Id = 1, NotificationListId = 1 }
+            });
+        _repository.GetAllSmtpConfigurationsAsync(Arg.Any<CancellationToken>())
+            .Returns(new List<SmtpConfiguration> { EwsConfig() });
+        _ewsSender.SendAsync(Arg.Any<EwsSendRequest>(), Arg.Any<CancellationToken>())
+            .ThrowsAsync(new OperationCanceledException(cts.Token));
+        var adapter = CreateAdapter();
+
+        await Assert.ThrowsAnyAsync<OperationCanceledException>(
+            () => adapter.DeliverAsync(MakeNotification(), cts.Token));
+    }
+
+    [Fact]
+    public async Task Deliver_NonHttpsEndpoint_ReturnsPermanentWithoutCallingSender()
+    {
+        SetupWithConfig(EwsConfig(host: "http://ews.example.test/ews/exchange.asmx"));
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        Assert.Equal(DeliveryResult.PermanentFailure, outcome.Result);
+        Assert.Contains("https", outcome.Error);
+        await AssertSenderUntouched();
+    }
+
+    [Fact]
+    public async Task Deliver_NonAbsoluteEndpoint_ReturnsPermanentWithoutCallingSender()
+    {
+        SetupWithConfig(EwsConfig(host: "ews.example.test"));
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        Assert.Equal(DeliveryResult.PermanentFailure, outcome.Result);
+        Assert.Contains("ews.example.test", outcome.Error);
+        await AssertSenderUntouched();
+    }
+
+    [Fact]
+    public async Task Deliver_NonBasicAuthType_ReturnsPermanentWithoutCallingSender()
+    {
+        SetupWithConfig(EwsConfig(authType: "oauth2"));
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        Assert.Equal(DeliveryResult.PermanentFailure, outcome.Result);
+        Assert.Contains("Basic", outcome.Error, StringComparison.OrdinalIgnoreCase);
+        await AssertSenderUntouched();
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("no-colon-here")]
+    [InlineData(":pw")]
+    [InlineData(@"dom\svc:")]
+    public async Task Deliver_MalformedCredentials_ReturnsPermanentWithoutCallingSender(
+        string? credentials)
+    {
+        SetupWithConfig(EwsConfig(credentials: credentials));
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        Assert.Equal(DeliveryResult.PermanentFailure, outcome.Result);
+        Assert.Contains("username:password", outcome.Error);
+        await AssertSenderUntouched();
+    }
+
+    [Fact]
+    public async Task Deliver_UnknownTransport_ReturnsPermanentWithoutCallingSender()
+    {
+        SetupWithConfig(EwsConfig(transport: "Graph"));
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        Assert.Equal(DeliveryResult.PermanentFailure, outcome.Result);
+        Assert.Contains("Graph", outcome.Error);
+        await AssertSenderUntouched();
+        await _smtpClient.DidNotReceive().ConnectAsync(
+            Arg.Any<string>(), Arg.Any<int>(), Arg.Any<SmtpTlsMode>(),
+            Arg.Any<int>(), Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task Deliver_NoEwsSenderRegistered_ReturnsPermanent()
+    {
+        SetupWithConfig(EwsConfig());
+        var adapter = CreateAdapter(withEwsSender: false);
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        Assert.Equal(DeliveryResult.PermanentFailure, outcome.Result);
+        Assert.Contains("EWS", outcome.Error);
+        Assert.Contains("registered", outcome.Error);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("Smtp")]
+    public async Task Deliver_SmtpOrUnsetTransport_TakesSmtpPath(string? transport)
+    {
+        SetupWithConfig(SmtpConfig(transport));
+        var adapter = CreateAdapter();
+
+        var outcome = await adapter.DeliverAsync(MakeNotification());
+
+        Assert.Equal(DeliveryResult.Success, outcome.Result);
+        await _smtpClient.Received().ConnectAsync(
+            "smtp.example.com", 587, SmtpTlsMode.StartTls,
+            Arg.Any<int>(), Arg.Any<CancellationToken>());
+        await AssertSenderUntouched();
+    }
+}