fix(notification): save smtp sender without reentering password

Preserve the saved SMTP password when connection settings are unchanged and keep it out of admin forms.

Ref: IT-1601

HrynCo.NotificationService.Web.IntegrationTests/AdminSmtpEditorViewTests.cs

@@ -0,0 +1,34 @@
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.EF;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class AdminSmtpEditorViewTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task ExistingChannelTestIncludesIdWithoutRenderingSavedPassword()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        using var scope = context.App.Services.CreateScope();
+        var channel = new EmailChannel
+        {
+            ServiceName = "TestService",
+            EmailChannelType = EmailChannelType.Smtp,
+            Settings = new SmtpChannelSettings
+            {
+                Host = "smtp.example.invalid", Username = "test-user",
+                Password = "saved-secret-must-not-render", FromEmail = "sender@example.invalid"
+            }
+        };
+        await scope.ServiceProvider.GetRequiredService<IEmailChannelRepository>().AddAsync(channel);
+        await scope.ServiceProvider.GetRequiredService<NotificationDbContext>().SaveChangesAsync();
+
+        var html = await context.Client.GetStringAsync($"/admin/channels/{channel.Id}");
+
+        Assert.Contains($"value=\"{channel.Id}\"", html);
+        Assert.Contains("const channelId = form.querySelector('[name=\"Id\"]').value", html);
+        Assert.DoesNotContain("saved-secret-must-not-render", html);
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/AdminSmtpSaveTests.cs

@@ -0,0 +1,136 @@
+using System.Net;
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.EF;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class AdminSmtpSaveTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task BlankPasswordKeepsSavedValueWhenOnlySenderChanges()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var channel = await SeedChannel(context);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync($"/admin/channels/{channel.Id}"));
+        fields["UseSsl"] = "true";
+        fields["Password"] = "";
+        fields["FromName"] = "Updated sender";
+
+        var response = await client.PostAsync("/admin/channels/save", new FormUrlEncodedContent(fields));
+
+        Assert.Equal(HttpStatusCode.Redirect, response.StatusCode);
+        var saved = await ReadSettings(context, channel.Id);
+        Assert.Equal("saved-test-secret", saved.Password);
+        Assert.Equal("Updated sender", saved.FromName);
+    }
+
+    [Theory]
+    [InlineData("Host", "other.example.invalid")]
+    [InlineData("Port", "2525")]
+    [InlineData("Username", "other-user")]
+    [InlineData("UseSsl", "false")]
+    public async Task ChangedConnectionWithBlankPasswordIsRejected(string field, string value)
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var channel = await SeedChannel(context);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync($"/admin/channels/{channel.Id}"));
+        fields["UseSsl"] = "true";
+        fields["Password"] = "";
+        fields[field] = value;
+
+        var response = await client.PostAsync("/admin/channels/save", new FormUrlEncodedContent(fields));
+        var html = await response.Content.ReadAsStringAsync();
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Contains("Enter the password to save changed SMTP connection settings.", html);
+        Assert.DoesNotContain("saved-test-secret", html);
+        var saved = await ReadSettings(context, channel.Id);
+        Assert.Equal("saved-test-secret", saved.Password);
+        Assert.Equal("smtp.example.invalid", saved.Host);
+    }
+
+    [Fact]
+    public async Task ExplicitPasswordCanReplaceSavedValue()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var channel = await SeedChannel(context);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync($"/admin/channels/{channel.Id}"));
+        fields["UseSsl"] = "true";
+        fields["Password"] = "replacement-test-secret";
+        fields["Host"] = "other.example.invalid";
+
+        var response = await client.PostAsync("/admin/channels/save", new FormUrlEncodedContent(fields));
+
+        Assert.Equal(HttpStatusCode.Redirect, response.StatusCode);
+        var saved = await ReadSettings(context, channel.Id);
+        Assert.Equal("replacement-test-secret", saved.Password);
+        Assert.Equal("other.example.invalid", saved.Host);
+    }
+
+    [Fact]
+    public async Task NewChannelStillRequiresPassword()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync("/admin/channels/create"));
+        fields["ServiceName"] = "NewTestService";
+        fields["Host"] = "smtp.example.invalid";
+        fields["Username"] = "test-user";
+        fields["FromEmail"] = "sender@example.invalid";
+        fields["FromName"] = "Sender";
+        fields["Password"] = "";
+
+        var response = await client.PostAsync("/admin/channels/save", new FormUrlEncodedContent(fields));
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Contains("The Password field is required.", await response.Content.ReadAsStringAsync());
+    }
+
+    [Fact]
+    public async Task InvalidFormDoesNotRenderEnteredPassword()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var channel = await SeedChannel(context);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync($"/admin/channels/{channel.Id}"));
+        fields["Password"] = "replacement-test-secret";
+        fields["FromEmail"] = "invalid-address";
+
+        var response = await client.PostAsync("/admin/channels/save", new FormUrlEncodedContent(fields));
+        var html = await response.Content.ReadAsStringAsync();
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.DoesNotContain("replacement-test-secret", html);
+        Assert.Equal("saved-test-secret", (await ReadSettings(context, channel.Id)).Password);
+    }
+
+    private static async Task<EmailChannel> SeedChannel(DefinitionApiTestContext context)
+    {
+        using var scope = context.App.Services.CreateScope();
+        var channel = new EmailChannel
+        {
+            ServiceName = "TestService", EmailChannelType = EmailChannelType.Smtp,
+            Settings = new SmtpChannelSettings
+            {
+                Host = "smtp.example.invalid", Port = 587, Username = "test-user",
+                Password = "saved-test-secret", UseSsl = true,
+                FromEmail = "sender@example.invalid", FromName = "Original sender"
+            }
+        };
+        await scope.ServiceProvider.GetRequiredService<IEmailChannelRepository>().AddAsync(channel);
+        await scope.ServiceProvider.GetRequiredService<NotificationDbContext>().SaveChangesAsync();
+        return channel;
+    }
+
+    private static async Task<SmtpChannelSettings> ReadSettings(DefinitionApiTestContext context, Guid id)
+    {
+        using var scope = context.App.Services.CreateScope();
+        var channel = await scope.ServiceProvider.GetRequiredService<IEmailChannelRepository>().GetByIdAsync(id);
+        return Assert.IsType<SmtpChannelSettings>(channel?.Settings);
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/AdminSmtpTestControllerTests.cs

@@ -0,0 +1,112 @@
+using System.Reflection;
+using System.Text.Json;
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.Web.Controllers.Admin;
+using MediatR;
+using Microsoft.AspNetCore.Mvc;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class AdminSmtpTestControllerTests
+{
+    private static readonly Guid ChannelId = Guid.NewGuid();
+
+    [Fact]
+    public async Task BlankPasswordUsesSavedSecretAndCurrentUnsavedSender()
+    {
+        var (controller, recorder) = CreateController();
+        var response = await controller.TestSmtp(Request(), CancellationToken.None);
+
+        Assert.True(Succeeded(response));
+        Assert.Equal("saved-test-secret", recorder.SentCommand?.Password);
+        Assert.Equal("changed@example.invalid", recorder.SentCommand?.FromEmail);
+        Assert.Equal("Changed sender", recorder.SentCommand?.FromName);
+        Assert.Equal(1, recorder.LookupCount);
+        Assert.DoesNotContain("saved-test-secret", JsonSerializer.Serialize(((OkObjectResult)response).Value));
+    }
+
+    [Fact]
+    public async Task ExplicitPasswordOverridesSavedWithoutLookup()
+    {
+        var (controller, recorder) = CreateController();
+        var response = await controller.TestSmtp(Request() with { Password = "typed-test-secret" }, CancellationToken.None);
+
+        Assert.True(Succeeded(response));
+        Assert.Equal("typed-test-secret", recorder.SentCommand?.Password);
+        Assert.Equal(0, recorder.LookupCount);
+    }
+
+    [Theory]
+    [InlineData("host")]
+    [InlineData("port")]
+    [InlineData("username")]
+    [InlineData("ssl")]
+    public async Task ChangedConnectionRequiresExplicitPassword(string field)
+    {
+        var (controller, recorder) = CreateController();
+        var request = field switch
+        {
+            "host" => Request() with { Host = "other.example.invalid" },
+            "port" => Request() with { Port = 2525 },
+            "username" => Request() with { Username = "other-user" },
+            _ => Request() with { UseSsl = false }
+        };
+
+        var response = await controller.TestSmtp(request, CancellationToken.None);
+
+        Assert.False(Succeeded(response));
+        Assert.Null(recorder.SentCommand);
+    }
+
+    [Fact]
+    public async Task UnknownChannelDoesNotSend()
+    {
+        var (controller, recorder) = CreateController();
+        recorder.Channel = null;
+
+        var response = await controller.TestSmtp(Request(), CancellationToken.None);
+
+        Assert.False(Succeeded(response));
+        Assert.Null(recorder.SentCommand);
+    }
+
+    [Fact]
+    public async Task NewChannelKeepsAdHocTestBehavior()
+    {
+        var (controller, recorder) = CreateController();
+
+        var response = await controller.TestSmtp(Request() with { ChannelId = null }, CancellationToken.None);
+
+        Assert.True(Succeeded(response));
+        Assert.Equal(string.Empty, recorder.SentCommand?.Password);
+        Assert.Equal(0, recorder.LookupCount);
+    }
+
+    private static (AdminChannelsController Controller, RecordingAdminSmtpMediator Recorder) CreateController()
+    {
+        var mediator = DispatchProxy.Create<IMediator, RecordingAdminSmtpMediator>();
+        var recorder = (RecordingAdminSmtpMediator)mediator;
+        recorder.Channel = new EmailChannel
+        {
+            Id = ChannelId,
+            ServiceName = "TestService",
+            EmailChannelType = EmailChannelType.Smtp,
+            Settings = new SmtpChannelSettings
+            {
+                Host = "smtp.example.invalid", Port = 587,
+                Username = "test-user", Password = "saved-test-secret", UseSsl = true
+            }
+        };
+        return (new AdminChannelsController(mediator), recorder);
+    }
+
+    private static TestSmtpRequest Request() => new(
+        "smtp.example.invalid", 587, "test-user", "", true,
+        "changed@example.invalid", "Changed sender", "recipient@example.invalid", ChannelId);
+
+    private static bool Succeeded(IActionResult response)
+    {
+        var body = JsonSerializer.Serialize(((OkObjectResult)response).Value);
+        return JsonDocument.Parse(body).RootElement.GetProperty("success").GetBoolean();
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/RecordingAdminSmtpMediator.cs

@@ -0,0 +1,43 @@
+using System.Reflection;
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.EmailChannels.Get;
+using HrynCo.NotificationService.Services.EmailChannels.TestSmtp;
+using MediatR;
+using ServiceUnit = HrynCo.NotificationService.Services.Core.Unit;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public class RecordingAdminSmtpMediator : DispatchProxy
+{
+    public EmailChannel? Channel { get; set; }
+    public TestSmtpCommand? SentCommand { get; private set; }
+    public int LookupCount { get; private set; }
+
+    protected override object Invoke(MethodInfo? targetMethod, object?[]? args)
+    {
+        if (targetMethod?.Name != nameof(IMediator.Send) || args?.Length is null or 0)
+            throw new NotSupportedException();
+
+        return args[0] switch
+        {
+            GetEmailChannelQuery => RecordLookup(),
+            TestSmtpCommand command => RecordSend(command),
+            _ => throw new NotSupportedException()
+        };
+    }
+
+    private Task<ServiceResult<EmailChannel>> RecordLookup()
+    {
+        LookupCount++;
+        return Task.FromResult(Channel is null
+            ? ServiceResult<EmailChannel>.Failure("Channel not found.")
+            : ServiceResult<EmailChannel>.Success(Channel));
+    }
+
+    private Task<ServiceResult<ServiceUnit>> RecordSend(TestSmtpCommand command)
+    {
+        SentCommand = command;
+        return Task.FromResult(ServiceResult<ServiceUnit>.Success(ServiceUnit.Value));
+    }
+}

HrynCo.NotificationService.Web/Controllers/Admin/AdminChannelsController.cs

@@ -65,7 +65,6 @@ public class AdminChannelsController(IMediator mediator) : Controller
             Host = smtp.Host,
             Port = smtp.Port,
             Username = smtp.Username,
-            Password = smtp.Password,
             UseSsl = smtp.UseSsl,
             FromEmail = smtp.FromEmail,
             FromName = smtp.FromName
@@ -80,14 +79,21 @@ public class AdminChannelsController(IMediator mediator) : Controller
     public async Task<IActionResult> Save(EmailChannelEditViewModel model, CancellationToken ct)
     {
         if (!ModelState.IsValid)
-            return View("Edit", model);
+            return EditWithErrors(model);
+
+        var (password, passwordError) = await ResolvePasswordForSave(model, ct);
+        if (passwordError is not null)
+        {
+            ModelState.AddModelError(nameof(model.Password), passwordError);
+            return EditWithErrors(model);
+        }
 
         var smtpSettings = new SmtpChannelSettings
         {
             Host = model.Host,
             Port = model.Port,
             Username = model.Username,
-            Password = model.Password,
+            Password = password,
             UseSsl = model.UseSsl,
             FromEmail = model.FromEmail,
             FromName = model.FromName
@@ -109,7 +115,7 @@ public class AdminChannelsController(IMediator mediator) : Controller
             if (!result.IsSuccess)
             {
                 ModelState.AddModelError("", result.Error?.Message ?? "Failed to create channel.");
-                return View("Edit", model);
+                return EditWithErrors(model);
             }
         }
         else
@@ -127,19 +133,55 @@ public class AdminChannelsController(IMediator mediator) : Controller
             if (!result.IsSuccess)
             {
                 ModelState.AddModelError("", result.Error?.Message ?? "Failed to update channel.");
-                return View("Edit", model);
+                return EditWithErrors(model);
             }
         }
 
         return RedirectToAction(nameof(Index));
     }
 
+    private async Task<(string Password, string? Error)> ResolvePasswordForSave(
+        EmailChannelEditViewModel model, CancellationToken ct)
+    {
+        if (!string.IsNullOrEmpty(model.Password))
+            return (model.Password, null);
+        if (model.IsNew)
+            return ("", "The Password field is required.");
+
+        var channelResult = await mediator.Send(new GetEmailChannelQuery(model.Id), ct);
+        if (!channelResult.IsSuccess || channelResult.Result?.Settings is not SmtpChannelSettings saved)
+            return ("", "SMTP channel not found.");
+        if (!MatchesSavedSmtpConnection(model.Host, model.Port, model.Username, model.UseSsl, saved))
+            return ("", "Enter the password to save changed SMTP connection settings.");
+
+        return (saved.Password, null);
+    }
+
+    private IActionResult EditWithErrors(EmailChannelEditViewModel model)
+    {
+        model.Password = null;
+        return View("Edit", model);
+    }
+
     // POST /admin/channels/test-smtp
     [HttpPost("test-smtp")]
     public async Task<IActionResult> TestSmtp([FromBody] TestSmtpRequest request, CancellationToken ct)
     {
+        var password = request.Password;
+        if (string.IsNullOrEmpty(password) && request.ChannelId is Guid channelId)
+        {
+            var channelResult = await mediator.Send(new GetEmailChannelQuery(channelId), ct);
+            if (!channelResult.IsSuccess || channelResult.Result?.Settings is not SmtpChannelSettings saved)
+                return Ok(new { success = false, message = "SMTP channel not found." });
+
+            if (!MatchesSavedSmtpConnection(request.Host, request.Port, request.Username, request.UseSsl, saved))
+                return Ok(new { success = false, message = "Enter the password to test changed SMTP connection settings." });
+
+            password = saved.Password;
+        }
+
         var result = await mediator.Send(new TestSmtpCommand(
-            request.Host, request.Port, request.Username, request.Password,
+            request.Host, request.Port, request.Username, password ?? string.Empty,
             request.UseSsl, request.FromEmail, request.FromName, request.ToEmail), ct);
 
         if (!result.IsSuccess)
@@ -148,6 +190,13 @@ public class AdminChannelsController(IMediator mediator) : Controller
         return Ok(new { success = true, message = $"Test email sent to {request.ToEmail}." });
     }
 
+    private static bool MatchesSavedSmtpConnection(
+        string host, int port, string username, bool useSsl, SmtpChannelSettings saved) =>
+        string.Equals(host, saved.Host, StringComparison.OrdinalIgnoreCase)
+        && port == saved.Port
+        && string.Equals(username, saved.Username, StringComparison.Ordinal)
+        && useSsl == saved.UseSsl;
+
     // POST /admin/channels/{id}/test
     [HttpPost("{id:guid}/test")]
     public async Task<IActionResult> Test(Guid id, [FromBody] TestChannelRequest request, CancellationToken ct)
@@ -180,6 +229,3 @@ public class AdminChannelsController(IMediator mediator) : Controller
 }
 
 public record TestChannelRequest(string ToEmail);
-public record TestSmtpRequest(
-    string Host, int Port, string Username, string Password,
-    bool UseSsl, string FromEmail, string FromName, string ToEmail);

HrynCo.NotificationService.Web/Controllers/Admin/TestSmtpRequest.cs

@@ -0,0 +1,6 @@
+namespace HrynCo.NotificationService.Web.Controllers.Admin;
+
+public record TestSmtpRequest(
+    string Host, int Port, string Username, string Password,
+    bool UseSsl, string FromEmail, string FromName, string ToEmail,
+    Guid? ChannelId = null);

HrynCo.NotificationService.Web/Controllers/Admin/ViewModels/EmailChannelEditViewModel.cs

@@ -34,8 +34,7 @@ public class EmailChannelEditViewModel
     [Required]
     public string Username { get; set; } = "";
 
-    [Required]
+    public string? Password { get; set; }
-    public string Password { get; set; } = "";
 
     public bool UseSsl { get; set; } = true;
 

HrynCo.NotificationService.Web/Views/AdminChannels/Edit.cshtml

@@ -94,6 +94,10 @@
             <label asp-for="Password" class="form-label fw-semibold">Password</label>
             <input asp-for="Password" class="form-control" type="password" autocomplete="new-password" />
             <span asp-validation-for="Password" class="text-danger small"></span>
+            @if (!Model.IsNew)
+            {
+                <div class="form-text">Leave blank to keep the saved password when SMTP connection settings are unchanged.</div>
+            }
         </div>
     </div>
 
@@ -138,7 +142,7 @@
                 <button type="button" class="btn-close" data-bs-dismiss="modal"></button>
             </div>
             <div class="modal-body">
-                <p class="text-muted small">Tests the current form settings — no need to save first.</p>
+                <p class="text-muted small">Tests the current form settings — no need to save first. For an existing channel, a blank password uses the saved password only when the SMTP connection settings are unchanged.</p>
                 <label for="testToEmail" class="form-label fw-semibold">Recipient Email</label>
                 <input type="email" id="testToEmail" class="form-control" placeholder="you@example.com" />
                 <div id="testResult" class="mt-3" style="display:none"></div>
@@ -173,7 +177,9 @@
         }
 
         const form = document.getElementById('channelForm');
+        const channelId = form.querySelector('[name="Id"]').value;
         const payload = {
+            channelId: channelId === '00000000-0000-0000-0000-000000000000' ? null : channelId,
             host: form.querySelector('[name="Host"]').value,
             port: parseInt(form.querySelector('[name="Port"]').value, 10),
             username: form.querySelector('[name="Username"]').value,

docker/kubernetes/shared-notification/README.md

@@ -80,6 +80,17 @@ published, accepted by the Gmail SMTP channel, acknowledged as delivery successe
 Invemory Outbox, and confirmed in the recipient's Gmail conversation. Today's channel
 usage increased by two. Both queues ended with zero ready and unacknowledged messages.
 
+### Administrative SMTP test from Web — 2026-10-18
+
+The channel editor's **Send Test Email** action sends directly from Web through SMTP;
+it does not use the Worker or RabbitMQ. Its TCP 587 connection timed out while the
+production network policy allowed external SMTP only from Worker. The additive
+`web-to-external-smtp` policy in `production-network.yaml` grants Web the same public
+IPv4 TCP 587 egress as Worker, with the same private and cluster address exclusions.
+Apply this production overlay separately from the sandbox-only `notification.py`
+render. No SMTP credentials, channel settings, templates, or workload restart are
+required for this network change.
+
 The activation helper also persists the production user, queue and expanded Worker ACL
 in the `rabbit-definitions` Secret. The private password and matching RabbitMQ hash
 are saved with mode `0600`; updated `notification.py` reproduces that Secret during

docker/kubernetes/shared-notification/production-network.yaml

@@ -83,3 +83,32 @@ spec:
       ports:
         - protocol: TCP
           port: 587
+---
+apiVersion: networking.k8s.io/v1
+kind: NetworkPolicy
+metadata:
+  name: web-to-external-smtp
+  namespace: shared-notification
+spec:
+  podSelector:
+    matchLabels:
+      app.kubernetes.io/component: web
+      app.kubernetes.io/name: hrynco-shared-notification
+      app.kubernetes.io/managed-by: hrynco-shared-notification
+  policyTypes: [Egress]
+  egress:
+    - to:
+        - ipBlock:
+            cidr: 0.0.0.0/0
+            except:
+              - 10.0.0.0/8
+              - 100.64.0.0/10
+              - 127.0.0.0/8
+              - 169.254.0.0/16
+              - 172.16.0.0/12
+              - 192.168.0.0/16
+              - 224.0.0.0/4
+              - 240.0.0.0/4
+      ports:
+        - protocol: TCP
+          port: 587

docs/email-template-definition-api.md

@@ -73,6 +73,10 @@ The service/catalog lookup, validation, revision check, explicit removals, trans
 
 ## Email channels
 
+In the admin channel editor, **Send Test Email** tests the form's current values without saving them. An explicitly entered password takes precedence. When the password field is blank for an existing channel, the Web server reads its saved password only if host, port, username, and SSL/TLS mode still match the saved SMTP connection. Changed connection settings require an explicit password. The saved password is not placed in the page or test response. A new channel keeps the ad-hoc test behavior, including unauthenticated SMTP when username and password are empty.
+
+Saving an existing channel follows the same password rule: a blank password keeps the saved value when host, port, username, and SSL/TLS mode are unchanged, so sender name/address and limit edits do not require re-entering it. A changed SMTP connection needs an explicitly entered password. Creating a channel in the admin editor still requires a password. Validation errors redisplay the editor without rendering the saved or submitted password.
+
 - `GET /api/v1/email-channels/all` enumerates **all** channels, including channels whose exact `serviceName` has no service row.
 - Existing `GET /api/v1/email-channels?serviceName={exactName}`, GET by ID, POST, PUT by ID and DELETE by ID remain available. Create returns 201/Location and its existing GUID response; update/delete return 200/Unit.
 - Create supports SMTP (`channelType: 1`). Request/response `settings` explicitly maps `host`, `port`, `username`, `password`, `useSsl`, `fromEmail`, and `fromName`; reads no longer lose derived SMTP fields through an abstract JSON type. Host/fromEmail and a valid port are required. The optional empty username/password support unauthenticated development SMTP.