Feature: Add Chaos functionality to test integration handling of SMTP error responses (#402, #110, #144 & #268)

Closes #405

README.md

@@ -48,6 +48,7 @@ including image thumbnails), including optional [HTTPS](https://mailpit.axllent.
 - [SMTP relaying](https://mailpit.axllent.org/docs/configuration/smtp-relay/) (message release) - relay messages via a different SMTP server including an optional allowlist of accepted recipients
 - Fast message [storing & processing](https://mailpit.axllent.org/docs/configuration/email-storage/) - ingesting 100-200 emails per second over SMTP depending on CPU, network speed & email size,
 easily handling tens of thousands of emails, with automatic email pruning (by default keeping the most recent 500 emails)
+- [Chaos](ttps://mailpit.axllent.org/docs/integration/chaos/) feature to enable configurable SMTP errors to test application resilience
 - `List-Unsubscribe` syntax validation
 - Optional [webhook](https://mailpit.axllent.org/docs/integration/webhook/) for received messages
 

cmd/root.go

@@ -10,6 +10,7 @@ import (
 	"github.com/axllent/mailpit/internal/auth"
 	"github.com/axllent/mailpit/internal/logger"
 	"github.com/axllent/mailpit/internal/smtpd"
+	"github.com/axllent/mailpit/internal/smtpd/chaos"
 	"github.com/axllent/mailpit/internal/storage"
 	"github.com/axllent/mailpit/internal/tools"
 	"github.com/axllent/mailpit/server"
@@ -122,6 +123,10 @@ func init() {
 	rootCmd.Flags().BoolVar(&config.SMTPRelayAll, "smtp-relay-all", config.SMTPRelayAll, "Auto-relay all new messages via external SMTP server (caution!)")
 	rootCmd.Flags().StringVar(&config.SMTPRelayMatching, "smtp-relay-matching", config.SMTPRelayMatching, "Auto-relay new messages to only matching recipients (regular expression)")
 
+	// Chaos
+	rootCmd.Flags().BoolVar(&chaos.Enabled, "enable-chaos", chaos.Enabled, "Enable Chaos functionality (API / web UI)")
+	rootCmd.Flags().StringVar(&config.ChaosTriggers, "chaos-triggers", config.ChaosTriggers, "Enable Chaos & set the triggers for SMTP server")
+
 	// POP3 server
 	rootCmd.Flags().StringVar(&config.POP3Listen, "pop3", config.POP3Listen, "POP3 server bind interface and port")
 	rootCmd.Flags().StringVar(&config.POP3AuthFile, "pop3-auth-file", config.POP3AuthFile, "A password file for POP3 server authentication (enables POP3 server)")
@@ -281,6 +286,10 @@ func initConfigFromEnv() {
 	config.SMTPRelayConfig.AllowedRecipients = os.Getenv("MP_SMTP_RELAY_ALLOWED_RECIPIENTS")
 	config.SMTPRelayConfig.BlockedRecipients = os.Getenv("MP_SMTP_RELAY_BLOCKED_RECIPIENTS")
 
+	// Chaos
+	chaos.Enabled = getEnabledFromEnv("MP_ENABLE_CHAOS")
+	config.ChaosTriggers = os.Getenv("MP_CHAOS_TRIGGERS")
+
 	// POP3 server
 	if len(os.Getenv("MP_POP3_BIND_ADDR")) > 0 {
 		config.POP3Listen = os.Getenv("MP_POP3_BIND_ADDR")

config/config.go

@@ -15,6 +15,7 @@ import (
 
 	"github.com/axllent/mailpit/internal/auth"
 	"github.com/axllent/mailpit/internal/logger"
+	"github.com/axllent/mailpit/internal/smtpd/chaos"
 	"github.com/axllent/mailpit/internal/spamassassin"
 	"github.com/axllent/mailpit/internal/tools"
 	"gopkg.in/yaml.v3"
@@ -176,6 +177,9 @@ var (
 	// RepoBinaryName on Github for updater
 	RepoBinaryName = "mailpit"
 
+	// ChaosTriggers are parsed and set in the chaos module
+	ChaosTriggers string
+
 	// DisableHTMLCheck DEPRECATED 2024/04/13 - kept here to display console warning only
 	DisableHTMLCheck = false
 
@@ -344,6 +348,14 @@ func VerifyConfig() error {
 		return errors.New("[smtp] authentication requires STARTTLS or TLS encryption, run with `--smtp-auth-allow-insecure` to allow insecure authentication")
 	}
 
+	if err := parseChaosTriggers(); err != nil {
+		return fmt.Errorf("[chaos] %s", err.Error())
+	}
+
+	if chaos.Enabled {
+		logger.Log().Info("[chaos] is enabled")
+	}
+
 	// POP3 server
 	if POP3TLSCert != "" {
 		POP3TLSCert = filepath.Clean(POP3TLSCert)
@@ -602,6 +614,39 @@ func validateRelayConfig() error {
 	return nil
 }
 
+func parseChaosTriggers() error {
+	if ChaosTriggers == "" {
+		return nil
+	}
+
+	re := regexp.MustCompile(`^([a-zA-Z0-0]+):(\d\d\d):(\d+(\.\d)?)$`)
+
+	parts := strings.Split(ChaosTriggers, ",")
+	for _, p := range parts {
+		p = strings.TrimSpace(p)
+		if !re.MatchString(p) {
+			return fmt.Errorf("invalid argument: %s", p)
+		}
+
+		matches := re.FindAllStringSubmatch(p, 1)
+		key := matches[0][1]
+		errorCode, err := strconv.Atoi(matches[0][2])
+		if err != nil {
+			return err
+		}
+		probability, err := strconv.Atoi(matches[0][3])
+		if err != nil {
+			return err
+		}
+
+		if err := chaos.Set(key, errorCode, probability); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // IsFile returns whether a file exists and is readable
 func isFile(path string) bool {
 	f, err := os.Open(filepath.Clean(path))

internal/smtpd/chaos/chaos.go

@@ -0,0 +1,121 @@
+// Package chaos is used to simulate Chaos engineering (random failures) in the SMTPD server.
+// See https://en.wikipedia.org/wiki/Chaos_engineering
+// See https://mailpit.axllent.org/docs/integration/chaos/
+package chaos
+
+import (
+	"crypto/rand"
+	"fmt"
+	"math/big"
+	"strings"
+
+	"github.com/axllent/mailpit/internal/logger"
+)
+
+var (
+	// Enabled is a flag to enable or disable support for chaos
+	Enabled = false
+
+	// Config is the global Chaos configuration
+	Config = Triggers{
+		Sender:         Trigger{ErrorCode: 451, Probability: 0},
+		Recipient:      Trigger{ErrorCode: 451, Probability: 0},
+		Authentication: Trigger{ErrorCode: 535, Probability: 0},
+	}
+)
+
+// Triggers for the Chaos configuration
+//
+// swagger:model Triggers
+type Triggers struct {
+	// Sender trigger to fail on From, Sender
+	Sender Trigger
+	// Recipient trigger to fail on To, Cc, Bcc
+	Recipient Trigger
+	// Authentication trigger to fail while authenticating (auth must be configured)
+	Authentication Trigger
+}
+
+// Trigger for Chaos
+type Trigger struct {
+	// SMTP error code to return. The value must range from 400 to 599.
+	// required: true
+	// example: 451
+	ErrorCode int
+
+	// Probability (chance) of triggering the error. The value must range from 0 to 100.
+	// required: true
+	// example: 5
+	Probability int
+}
+
+// SetFromStruct will set a whole map of chaos configurations (ie: API)
+func SetFromStruct(c Triggers) error {
+	if c.Sender.ErrorCode == 0 {
+		c.Sender.ErrorCode = 451 // default
+	}
+
+	if c.Recipient.ErrorCode == 0 {
+		c.Recipient.ErrorCode = 451 // default
+	}
+
+	if c.Authentication.ErrorCode == 0 {
+		c.Authentication.ErrorCode = 535 // default
+	}
+
+	if err := Set("Sender", c.Sender.ErrorCode, c.Sender.Probability); err != nil {
+		return err
+	}
+	if err := Set("Recipient", c.Recipient.ErrorCode, c.Recipient.Probability); err != nil {
+		return err
+	}
+	if err := Set("Authentication", c.Authentication.ErrorCode, c.Authentication.Probability); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Set will set the chaos configuration for the given key (CLI & setMap())
+func Set(key string, errorCode int, probability int) error {
+	Enabled = true
+	if errorCode < 400 || errorCode > 599 {
+		return fmt.Errorf("error code must be between 400 and 599")
+	}
+
+	if probability > 100 || probability < 0 {
+		return fmt.Errorf("probability must be between 0 and 100")
+	}
+
+	key = strings.ToLower(key)
+
+	switch key {
+	case "sender":
+		Config.Sender = Trigger{ErrorCode: errorCode, Probability: probability}
+		logger.Log().Infof("[chaos] Sender to return %d error with %d%% probability", errorCode, probability)
+	case "recipient", "recipients":
+		Config.Recipient = Trigger{ErrorCode: errorCode, Probability: probability}
+		logger.Log().Infof("[chaos] Recipient to return %d error with %d%% probability", errorCode, probability)
+	case "auth", "authentication":
+		Config.Authentication = Trigger{ErrorCode: errorCode, Probability: probability}
+		logger.Log().Infof("[chaos] Authentication to return %d error with %d%% probability", errorCode, probability)
+	default:
+		return fmt.Errorf("unknown key %s", key)
+	}
+
+	return nil
+}
+
+// Trigger will return whether the Chaos rule is triggered based on the configuration
+// and a randomly-generated percentage value.
+func (c Trigger) Trigger() (bool, int) {
+	if !Enabled || c.Probability == 0 {
+		return false, 0
+	}
+
+	nBig, _ := rand.Int(rand.Reader, big.NewInt(100))
+
+	// rand.IntN(100) will return 0-99, whereas probability is 1-100,
+	// so value must be less than (not <=) to the probability to trigger
+	return int(nBig.Int64()) < c.Probability, c.ErrorCode
+}

internal/smtpd/smtpd.go

@@ -1,7 +1,7 @@
 // Package smtpd implements a basic SMTP server.
 //
 // This is a modified version of https://github.com/mhale/smtpd to
-// add optional support for unix sockets.
+// add support for unix sockets and Mailpit Chaos.
 package smtpd
 
 import (
@@ -22,6 +22,8 @@ import (
 	"sync"
 	"sync/atomic"
 	"time"
+
+	"github.com/axllent/mailpit/internal/smtpd/chaos"
 )
 
 var (
@@ -411,6 +413,12 @@ loop:
 			if match == nil {
 				s.writef("501 5.5.4 Syntax error in parameters or arguments (invalid FROM parameter)")
 			} else {
+				// Mailpit Chaos
+				if fail, code := chaos.Config.Sender.Trigger(); fail {
+					s.writef("%d Chaos sender error", code)
+					break
+				}
+
 				// Validate the SIZE parameter if one was sent.
 				if len(match[2]) > 0 { // A parameter is present
 					sizeMatch := mailFromSizeRE.FindStringSubmatch(match[3])
@@ -439,6 +447,7 @@ loop:
 					s.writef("250 2.1.0 Ok")
 				}
 			}
+
 			to = nil
 			buffer.Reset()
 		case "RCPT":
@@ -459,10 +468,17 @@ loop:
 			if match == nil {
 				s.writef("501 5.5.4 Syntax error in parameters or arguments (invalid TO parameter)")
 			} else {
+				// Mailpit Chaos
+				if fail, code := chaos.Config.Recipient.Trigger(); fail {
+					s.writef("%d Chaos recipient error", code)
+					break
+				}
+
 				// RFC 5321 specifies support for minimum of 100 recipients is required.
 				if s.srv.MaxRecipients == 0 {
 					s.srv.MaxRecipients = 100
 				}
+
 				if len(to) == s.srv.MaxRecipients {
 					s.writef("452 4.5.3 Too many recipients")
 				} else {
@@ -685,6 +701,12 @@ loop:
 				break
 			}
 
+			// Mailpit Chaos
+			if fail, code := chaos.Config.Authentication.Trigger(); fail {
+				s.writef("%d Chaos authentication error", code)
+				break
+			}
+
 			// RFC 4954 also specifies that ESMTP code 5.5.4 ("Invalid command arguments") should be returned
 			// when attempting to use an unsupported authentication type.
 			// Many servers return 5.7.4 ("Security features not supported") instead.

server/apiv1/application.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 
 	"github.com/axllent/mailpit/config"
+	"github.com/axllent/mailpit/internal/smtpd/chaos"
 	"github.com/axllent/mailpit/internal/stats"
 )
 
@@ -67,6 +68,9 @@ type webUIConfiguration struct {
 	// Whether SpamAssassin is enabled
 	SpamAssassin bool
 
+	// Whether Chaos support is enabled at runtime
+	ChaosEnabled bool
+
 	// Whether messages with duplicate IDs are ignored
 	DuplicatesIgnored bool
 }
@@ -112,6 +116,7 @@ func WebUIConfig(w http.ResponseWriter, _ *http.Request) {
 	}
 
 	conf.SpamAssassin = config.EnableSpamAssassin != ""
+	conf.ChaosEnabled = chaos.Enabled
 	conf.DuplicatesIgnored = config.IgnoreDuplicateIDs
 
 	w.Header().Add("Content-Type", "application/json")

server/apiv1/chaos.go

@@ -0,0 +1,112 @@
+package apiv1
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/axllent/mailpit/internal/smtpd/chaos"
+)
+
+// ChaosTriggers is the Chaos configuration
+//
+// swagger:model Triggers
+type ChaosTriggers chaos.Triggers
+
+// Response for the Chaos triggers configuration
+// swagger:response ChaosResponse
+type chaosResponse struct {
+	// The current Chaos triggers
+	//
+	// in: body
+	Body ChaosTriggers
+}
+
+// GetChaos returns the current Chaos triggers
+func GetChaos(w http.ResponseWriter, _ *http.Request) {
+	// swagger:route GET /api/v1/chaos testing getChaos
+	//
+	// # Get Chaos triggers
+	//
+	// Returns the current Chaos triggers configuration.
+	// This API route will return an error if Chaos is not enabled at runtime.
+	//
+	//	Produces:
+	//	  - application/json
+	//
+	//	Schemes: http, https
+	//
+	//	Responses:
+	//	  200: ChaosResponse
+	//	  400: ErrorResponse
+
+	if !chaos.Enabled {
+		httpError(w, "Chaos is not enabled")
+		return
+	}
+
+	conf := chaos.Config
+
+	w.Header().Add("Content-Type", "application/json")
+	if err := json.NewEncoder(w).Encode(conf); err != nil {
+		httpError(w, err.Error())
+	}
+}
+
+// swagger:parameters setChaosParams
+type setChaosParams struct {
+	// in: body
+	Body ChaosTriggers
+}
+
+// SetChaos sets the Chaos configuration.
+func SetChaos(w http.ResponseWriter, r *http.Request) {
+	// swagger:route PUT /api/v1/chaos testing setChaosParams
+	//
+	// # Set Chaos triggers
+	//
+	// Set the Chaos triggers configuration and return the updated values.
+	// This API route will return an error if Chaos is not enabled at runtime.
+	//
+	// If any triggers are omitted from the request, then those are reset to their
+	// default values with a 0% probability (ie: disabled).
+	// Setting a blank `{}` will reset all triggers to their default values.
+	//
+	//	Consumes:
+	//	  - application/json
+	//
+	//	Produces:
+	//	  - application/json
+	//
+	//	Schemes: http, https
+	//
+	//	Responses:
+	//	  200: ChaosResponse
+	//	  400: ErrorResponse
+
+	if !chaos.Enabled {
+		httpError(w, "Chaos is not enabled")
+		return
+	}
+
+	data := chaos.Triggers{}
+
+	decoder := json.NewDecoder(r.Body)
+
+	err := decoder.Decode(&data)
+	if err != nil {
+		httpError(w, err.Error())
+		return
+	}
+
+	if err := chaos.SetFromStruct(data); err != nil {
+		httpError(w, err.Error())
+		return
+	}
+
+	conf := chaos.Config
+
+	w.Header().Add("Content-Type", "application/json")
+	if err := json.NewEncoder(w).Encode(conf); err != nil {
+		httpError(w, err.Error())
+	}
+}

server/server.go

@@ -183,6 +183,10 @@ func apiRoutes() *mux.Router {
 	r.HandleFunc(config.Webroot+"api/v1/webui", middleWareFunc(apiv1.WebUIConfig)).Methods("GET")
 	r.HandleFunc(config.Webroot+"api/v1/swagger.json", middleWareFunc(swaggerBasePath)).Methods("GET")
 
+	// Chaos
+	r.HandleFunc(config.Webroot+"api/v1/chaos", middleWareFunc(apiv1.GetChaos)).Methods("GET")
+	r.HandleFunc(config.Webroot+"api/v1/chaos", middleWareFunc(apiv1.SetChaos)).Methods("PUT")
+
 	// web UI websocket
 	r.HandleFunc(config.Webroot+"api/events", apiWebsocket).Methods("GET")
 

server/ui-src/components/Settings.vue

@@ -12,6 +12,8 @@ export default {
 			mailbox,
 			theme: localStorage.getItem('theme') ? localStorage.getItem('theme') : 'auto',
 			timezones,
+			chaosConfig: false,
+			chaosUpdated: false,
 		}
 	},
 
@@ -23,6 +25,13 @@ export default {
 				localStorage.setItem('theme', v)
 			}
 			this.setTheme()
+		},
+
+		chaosConfig: {
+			handler() {
+				this.chaosUpdated = true
+			},
+			deep: true
 		}
 	},
 
@@ -44,6 +53,24 @@ export default {
 				document.documentElement.setAttribute('data-bs-theme', this.theme)
 			}
 		},
+
+		loadChaos() {
+			this.get(this.resolve('/api/v1/chaos'), null, (response) => {
+				this.chaosConfig = response.data
+				this.$nextTick(() => {
+					this.chaosUpdated = false
+				})
+			})
+		},
+
+		saveChaos() {
+			this.put(this.resolve('/api/v1/chaos'), this.chaosConfig, (response) => {
+				this.chaosConfig = response.data
+				this.$nextTick(() => {
+					this.chaosUpdated = false
+				})
+			})
+		}
 	}
 }
 </script>
@@ -54,64 +81,189 @@ export default {
 		<div class="modal-dialog modal-lg">
 			<div class="modal-content">
 				<div class="modal-header">
-					<h5 class="modal-title" id="SettingsModalLabel">Mailpit UI settings</h5>
+					<h5 class="modal-title" id="SettingsModalLabel">Mailpit settings</h5>
 					<button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close"></button>
 				</div>
 				<div class="modal-body">
-					<div class="mb-3">
-						<label for="theme" class="form-label">Mailpit theme</label>
-						<select class="form-select" v-model="theme" id="theme">
-							<option value="auto">Auto (detect from browser)</option>
-							<option value="light">Light theme</option>
-							<option value="dark">Dark theme</option>
-						</select>
-					</div>
-					<div class="mb-3">
-						<label for="timezone" class="form-label">Timezone (for date searches)</label>
-						<select class="form-select tz" v-model="mailbox.timeZone" id="timezone" data-allow-same="true">
-							<option disabled hidden value="">Select a timezone...</option>
-							<option v-for="t in timezones" :value="t.tzCode">{{ t.label }}</option>
-						</select>
-					</div>
-					<div class="mb-3">
-						<div class="form-check form-switch">
-							<input class="form-check-input" type="checkbox" role="switch" id="tagColors"
-								v-model="mailbox.showTagColors">
-							<label class="form-check-label" for="tagColors">
-								Use auto-generated tag colors
-							</label>
+					<ul class="nav nav-tabs" id="myTab" role="tablist" v-if="mailbox.uiConfig.ChaosEnabled">
+						<li class="nav-item" role="presentation">
+							<button class="nav-link active" id="ui-tab" data-bs-toggle="tab"
+								data-bs-target="#ui-tab-pane" type="button" role="tab" aria-controls="ui-tab-pane"
+								aria-selected="true">Web UI</button>
+						</li>
+						<li class="nav-item" role="presentation">
+							<button class="nav-link" id="chaos-tab" data-bs-toggle="tab"
+								data-bs-target="#chaos-tab-pane" type="button" role="tab" aria-controls="chaos-tab-pane"
+								aria-selected="false" @click="loadChaos">Chaos</button>
+						</li>
+					</ul>
+
+					<div class="tab-content">
+						<div class="tab-pane fade show active" id="ui-tab-pane" role="tabpanel" aria-labelledby="ui-tab"
+							tabindex="0">
+							<div class="my-3">
+								<label for="theme" class="form-label">Mailpit theme</label>
+								<select class="form-select" v-model="theme" id="theme">
+									<option value="auto">Auto (detect from browser)</option>
+									<option value="light">Light theme</option>
+									<option value="dark">Dark theme</option>
+								</select>
+							</div>
+							<div class="mb-3">
+								<label for="timezone" class="form-label">Timezone (for date searches)</label>
+								<select class="form-select tz" v-model="mailbox.timeZone" id="timezone"
+									data-allow-same="true">
+									<option disabled hidden value="">Select a timezone...</option>
+									<option v-for="t in timezones" :value="t.tzCode">{{ t.label }}</option>
+								</select>
+							</div>
+							<div class="mb-3">
+								<div class="form-check form-switch">
+									<input class="form-check-input" type="checkbox" role="switch" id="tagColors"
+										v-model="mailbox.showTagColors">
+									<label class="form-check-label" for="tagColors">
+										Use auto-generated tag colors
+									</label>
+								</div>
+							</div>
+							<div class="mb-3">
+								<div class="form-check form-switch">
+									<input class="form-check-input" type="checkbox" role="switch" id="htmlCheck"
+										v-model="mailbox.showHTMLCheck">
+									<label class="form-check-label" for="htmlCheck">
+										Show HTML check message tab
+									</label>
+								</div>
+							</div>
+							<div class="mb-3">
+								<div class="form-check form-switch">
+									<input class="form-check-input" type="checkbox" role="switch" id="linkCheck"
+										v-model="mailbox.showLinkCheck">
+									<label class="form-check-label" for="linkCheck">
+										Show link check message tab
+									</label>
+								</div>
+							</div>
+							<div class="mb-3" v-if="mailbox.uiConfig.SpamAssassin">
+								<div class="form-check form-switch">
+									<input class="form-check-input" type="checkbox" role="switch" id="spamCheck"
+										v-model="mailbox.showSpamCheck">
+									<label class="form-check-label" for="spamCheck">
+										Show spam check message tab
+									</label>
+								</div>
+							</div>
 						</div>
-					</div>
-					<div class="mb-3">
-						<div class="form-check form-switch">
-							<input class="form-check-input" type="checkbox" role="switch" id="htmlCheck"
-								v-model="mailbox.showHTMLCheck">
-							<label class="form-check-label" for="htmlCheck">
-								Show HTML check message tab
-							</label>
+
+						<div class="tab-pane fade" id="chaos-tab-pane" role="tabpanel" aria-labelledby="chaos-tab"
+							tabindex="0" v-if="mailbox.uiConfig.ChaosEnabled">
+							<p class="my-3">
+								<b>Chaos</b> allows you to set random SMTP failures and response codes at various
+								stages in a SMTP transaction to test application resilience
+								(<a href="https://mailpit.axllent.org/docs/integration/chaos/" target="_blank">
+									see documentation
+								</a>).
+							</p>
+
+							<ul>
+								<li>
+									<code>Response code</code> is the SMTP error code returned by the server if this
+									error is triggered. Error codes must range between 400 and 599.
+								</li>
+								<li>
+									<code>Error probability</code> is the % chance that the error will occur per message
+									delivery, where <code>0</code>(%) is disabled and <code>100</code>(%) wil always
+									trigger. A probability of <code>50</code> will trigger on approximately 50% of
+									messages received.
+								</li>
+							</ul>
+
+							<template v-if="chaosConfig">
+								<div class="mt-4 mb-4" :class="chaosUpdated ? 'was-validated' : ''">
+									<div class="mb-4">
+										<label>Trigger: <code>Sender</code></label>
+										<div class="form-text">
+											Trigger an error response based on the sender (From / Sender).
+										</div>
+										<div class="row mt-1">
+											<div class="col">
+												<label class="form-label">
+													Response code
+												</label>
+												<input type="number" class="form-control"
+													v-model.number="chaosConfig.Sender.ErrorCode" min="400" max="599"
+													required>
+											</div>
+											<div class="col">
+												<label class="form-label">
+													Error probability ({{ chaosConfig.Sender.Probability }}%)
+												</label>
+												<input type="range" class="form-range mt-1" min="0" max="100"
+													v-model.number="chaosConfig.Sender.Probability">
+											</div>
+										</div>
+									</div>
+
+									<div class="mb-4">
+										<label>Trigger: <code>Recipient</code></label>
+										<div class="form-text">
+											Trigger an error response based on the recipients (To, Cc, Bcc).
+										</div>
+										<div class="row mt-1">
+											<div class="col">
+												<label class="form-label">
+													Response code
+												</label>
+												<input type="number" class="form-control"
+													v-model.number="chaosConfig.Recipient.ErrorCode" min="400" max="599"
+													required>
+											</div>
+											<div class="col">
+												<label class="form-label">
+													Error probability ({{ chaosConfig.Recipient.Probability }}%)
+												</label>
+												<input type="range" class="form-range mt-1" min="0" max="100"
+													v-model.number="chaosConfig.Recipient.Probability">
+											</div>
+										</div>
+									</div>
+
+									<div class="mb-4">
+										<label>Trigger: <code>Authentication</code></label>
+										<div class="form-text">
+											Trigger an authentication error response.
+											Note that SMTP authentication must be configured too.
+										</div>
+										<div class="row mt-1">
+											<div class="col">
+												<label class="form-label">
+													Response code
+												</label>
+												<input type="number" class="form-control"
+													v-model.number="chaosConfig.Authentication.ErrorCode" min="400"
+													max="599" required>
+											</div>
+											<div class="col">
+												<label class="form-label">
+													Error probability ({{ chaosConfig.Authentication.Probability }}%)
+												</label>
+												<input type="range" class="form-range mt-1" min="0" max="100"
+													v-model.number="chaosConfig.Authentication.Probability">
+											</div>
+										</div>
+									</div>
+								</div>
+
+								<div v-if="chaosUpdated" class="mb-3 text-center">
+									<button class="btn btn-success" @click="saveChaos">Update Chaos</button>
+								</div>
+							</template>
 						</div>
+
 					</div>
-					<div class="mb-3">
-						<div class="form-check form-switch">
-							<input class="form-check-input" type="checkbox" role="switch" id="linkCheck"
-								v-model="mailbox.showLinkCheck">
-							<label class="form-check-label" for="linkCheck">
-								Show link check message tab
-							</label>
-						</div>
+					<div class="modal-footer">
+						<button type="button" class="btn btn-outline-secondary" data-bs-dismiss="modal">Close</button>
 					</div>
-					<div class="mb-3" v-if="mailbox.uiConfig.SpamAssassin">
-						<div class="form-check form-switch">
-							<input class="form-check-input" type="checkbox" role="switch" id="spamCheck"
-								v-model="mailbox.showSpamCheck">
-							<label class="form-check-label" for="spamCheck">
-								Show spam check message tab
-							</label>
-						</div>
-					</div>
-				</div>
-				<div class="modal-footer">
-					<button type="button" class="btn btn-outline-secondary" data-bs-dismiss="modal">Close</button>
 				</div>
 			</div>
 		</div>

server/ui/api/v1/swagger.json

@@ -23,6 +23,66 @@
     "version": "v1"
   },
   "paths": {
+    "/api/v1/chaos": {
+      "get": {
+        "description": "Returns the current Chaos triggers configuration.\nThis API route will return an error if Chaos is not enabled at runtime.",
+        "produces": [
+          "application/json"
+        ],
+        "schemes": [
+          "http",
+          "https"
+        ],
+        "tags": [
+          "testing"
+        ],
+        "summary": "Get Chaos triggers",
+        "operationId": "getChaos",
+        "responses": {
+          "200": {
+            "$ref": "#/responses/ChaosResponse"
+          },
+          "400": {
+            "$ref": "#/responses/ErrorResponse"
+          }
+        }
+      },
+      "put": {
+        "description": "Set the Chaos triggers configuration and return the updated values.\nThis API route will return an error if Chaos is not enabled at runtime.\n\nIf any triggers are omitted from the request, then those are reset to their\ndefault values with a 0% probability (ie: disabled).\nSetting a blank `{}` will reset all triggers to their default values.",
+        "consumes": [
+          "application/json"
+        ],
+        "produces": [
+          "application/json"
+        ],
+        "schemes": [
+          "http",
+          "https"
+        ],
+        "tags": [
+          "testing"
+        ],
+        "summary": "Set Chaos triggers",
+        "operationId": "setChaosParams",
+        "parameters": [
+          {
+            "name": "Body",
+            "in": "body",
+            "schema": {
+              "$ref": "#/definitions/Triggers"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "$ref": "#/responses/ChaosResponse"
+          },
+          "400": {
+            "$ref": "#/responses/ErrorResponse"
+          }
+        }
+      }
+    },
     "/api/v1/info": {
       "get": {
         "description": "Returns basic runtime information, message totals and latest release version.",
@@ -139,7 +199,7 @@
           "https"
         ],
         "tags": [
-          "Other"
+          "other"
         ],
         "summary": "HTML check",
         "operationId": "HTMLCheckParams",
@@ -179,7 +239,7 @@
           "https"
         ],
         "tags": [
-          "Other"
+          "other"
         ],
         "summary": "Link check",
         "operationId": "LinkCheckParams",
@@ -414,7 +474,7 @@
           "https"
         ],
         "tags": [
-          "Other"
+          "other"
         ],
         "summary": "SpamAssassin check",
         "operationId": "SpamAssassinCheckParams",
@@ -1816,10 +1876,54 @@
       "x-go-name": "Result",
       "x-go-package": "github.com/axllent/mailpit/internal/spamassassin"
     },
+    "Trigger": {
+      "description": "Trigger for Chaos",
+      "type": "object",
+      "required": [
+        "ErrorCode",
+        "Probability"
+      ],
+      "properties": {
+        "ErrorCode": {
+          "description": "SMTP error code to return. The value must range from 400 to 599.",
+          "type": "integer",
+          "format": "int64",
+          "example": 451
+        },
+        "Probability": {
+          "description": "Probability (chance) of triggering the error. The value must range from 0 to 100.",
+          "type": "integer",
+          "format": "int64",
+          "example": 5
+        }
+      },
+      "x-go-package": "github.com/axllent/mailpit/internal/smtpd/chaos"
+    },
+    "Triggers": {
+      "description": "ChaosTriggers is the Chaos configuration",
+      "type": "object",
+      "properties": {
+        "Authentication": {
+          "$ref": "#/definitions/Trigger"
+        },
+        "Recipient": {
+          "$ref": "#/definitions/Trigger"
+        },
+        "Sender": {
+          "$ref": "#/definitions/Trigger"
+        }
+      },
+      "x-go-package": "github.com/axllent/mailpit/internal/smtpd/chaos",
+      "$ref": "#/definitions/Triggers"
+    },
     "WebUIConfiguration": {
       "description": "Response includes global web UI settings",
       "type": "object",
       "properties": {
+        "ChaosEnabled": {
+          "description": "Whether Chaos support is enabled at runtime",
+          "type": "boolean"
+        },
         "DuplicatesIgnored": {
           "description": "Whether messages with duplicate IDs are ignored",
           "type": "boolean"
@@ -1885,6 +1989,12 @@
         "type": "string"
       }
     },
+    "ChaosResponse": {
+      "description": "Response for the Chaos triggers configuration",
+      "schema": {
+        "$ref": "#/definitions/Triggers"
+      }
+    },
     "ErrorResponse": {
       "description": "Server error will return with a 400 status code\nwith the error message in the body",
       "schema": {