diff --git a/cmd/oauth.go b/cmd/oauth.go
index e3dc9984..ca09a047 100644
--- a/cmd/oauth.go
+++ b/cmd/oauth.go
@@ -152,9 +152,9 @@ func handleOAuthCallback(r *fastglue.Request) error {
 	redirectURI := oauthData["redirect_uri"]
 	clientID := oauthData["client_id"]
 	clientSecret := oauthData["client_secret"]
-	tenantID := oauthData["tenant_id"]   // Empty string if not set
-	flowType := oauthData["flow_type"]   // "new_inbox" or "reconnect"
-	inboxIDStr := oauthData["inbox_id"]  // Inbox ID for reconnect flow
+	tenantID := oauthData["tenant_id"]  // Empty string if not set
+	flowType := oauthData["flow_type"]  // "new_inbox" or "reconnect"
+	inboxIDStr := oauthData["inbox_id"] // Inbox ID for reconnect flow
 
 	// Validate provider matches URL parameter
 	if storedProvider != provider {
@@ -310,11 +310,12 @@ func handleOAuthCallback(r *fastglue.Request) error {
 
 	// Create inbox config
 	config := imodels.Config{
-		SMTP:     []imodels.SMTPConfig{smtpConfig},
-		IMAP:     []imodels.IMAPConfig{imapConfig},
-		From:     userEmail,
-		AuthType: imodels.AuthTypeOAuth2,
-		OAuth:    oauthConfig,
+		SMTP:                 []imodels.SMTPConfig{smtpConfig},
+		IMAP:                 []imodels.IMAPConfig{imapConfig},
+		From:                 userEmail,
+		AuthType:             imodels.AuthTypeOAuth2,
+		OAuth:                oauthConfig,
+		EnablePlusAddressing: true,
 	}
 
 	configJSON, err := json.Marshal(config)
diff --git a/cmd/upgrade.go b/cmd/upgrade.go
index bb0cf3be..95ac5b56 100644
--- a/cmd/upgrade.go
+++ b/cmd/upgrade.go
@@ -39,6 +39,7 @@ var migList = []migFunc{
 	{"v0.8.5", migrations.V0_8_5},
 	{"v0.9.1", migrations.V0_9_1},
 	{"v0.10.0", migrations.V0_10_0},
+	{"v1.0.1", migrations.V1_0_1},
 }
 
 // upgrade upgrades the database to the current version by running SQL migration files
diff --git a/frontend/src/features/admin/inbox/EmailInboxForm.vue b/frontend/src/features/admin/inbox/EmailInboxForm.vue
index 232c4de6..9bc1bd13 100644
--- a/frontend/src/features/admin/inbox/EmailInboxForm.vue
+++ b/frontend/src/features/admin/inbox/EmailInboxForm.vue
@@ -54,11 +54,25 @@
           <Switch :checked="componentField.modelValue" @update:checked="handleChange" />
         </FormControl>
       </FormItem>
-      <p class="!mt-2 text-muted-foreground text-sm">
+      <p class="!mt-2 text-muted-foreground text-xs">
         {{ $t('admin.inbox.csatSurveys.description_2') }}
       </p>
     </FormField>
 
+    <FormField v-if="showFormFields" v-slot="{ componentField, handleChange }" name="enable_plus_addressing">
+      <FormItem class="flex flex-row items-center justify-between box p-4">
+        <div class="space-y-0.5">
+          <FormLabel class="text-base">{{ $t('admin.inbox.enablePlusAddressing') }}</FormLabel>
+          <FormDescription>
+            {{ $t('admin.inbox.enablePlusAddressing.description') }}
+          </FormDescription>
+        </div>
+        <FormControl>
+          <Switch :checked="componentField.modelValue" @update:checked="handleChange" />
+        </FormControl>
+      </FormItem>
+    </FormField>
+
     <FormField v-if="setupMethod" v-slot="{ componentField }" name="auth_type">
       <FormItem>
         <FormControl>
@@ -729,6 +743,7 @@ const form = useForm({
     from: '',
     enabled: true,
     csat_enabled: false,
+    enable_plus_addressing: true,
     auth_type: AUTH_TYPE_PASSWORD,
     imap: {
       host: 'imap.gmail.com',
diff --git a/frontend/src/features/admin/inbox/formSchema.js b/frontend/src/features/admin/inbox/formSchema.js
index 69d3db21..c5a22357 100644
--- a/frontend/src/features/admin/inbox/formSchema.js
+++ b/frontend/src/features/admin/inbox/formSchema.js
@@ -7,6 +7,7 @@ export const createFormSchema = (t) => z.object({
   from: z.string().min(1, t('globals.messages.required')),
   enabled: z.boolean().optional(),
   csat_enabled: z.boolean().optional(),
+  enable_plus_addressing: z.boolean().optional(),
   auth_type: z.enum([AUTH_TYPE_PASSWORD, AUTH_TYPE_OAUTH2]),
   oauth: z.object({
     access_token: z.string().optional(),
diff --git a/frontend/src/views/admin/inbox/EditInbox.vue b/frontend/src/views/admin/inbox/EditInbox.vue
index 9c914be2..2a4f18e2 100644
--- a/frontend/src/views/admin/inbox/EditInbox.vue
+++ b/frontend/src/views/admin/inbox/EditInbox.vue
@@ -32,6 +32,7 @@ const submitForm = (values) => {
   // Prepare request payload from form values
   const config = {
     auth_type: values.auth_type,
+    enable_plus_addressing: values.enable_plus_addressing,
     imap: [{ ...values.imap }],
     smtp: [{ ...values.smtp }]
   }
@@ -106,6 +107,7 @@ onMounted(async () => {
     }
     inboxData.auth_type = inboxData?.config?.auth_type || AUTH_TYPE_PASSWORD
     inboxData.oauth = inboxData?.config?.oauth || {}
+    inboxData.enable_plus_addressing = inboxData?.config?.enable_plus_addressing || false
     inbox.value = inboxData
   } catch (error) {
     emitter.emit(EMITTER_EVENTS.SHOW_TOAST, {
diff --git a/frontend/src/views/admin/inbox/NewInbox.vue b/frontend/src/views/admin/inbox/NewInbox.vue
index 1ac41435..e1a45f61 100644
--- a/frontend/src/views/admin/inbox/NewInbox.vue
+++ b/frontend/src/views/admin/inbox/NewInbox.vue
@@ -158,6 +158,7 @@ const submitForm = (values) => {
     from: values.from,
     channel: channelName,
     config: {
+      enable_plus_addressing: values.enable_plus_addressing,
       imap: [values.imap],
       smtp: [values.smtp]
     }
diff --git a/i18n/en.json b/i18n/en.json
index 2f8b62d2..70b0b93b 100644
--- a/i18n/en.json
+++ b/i18n/en.json
@@ -511,6 +511,8 @@
   "admin.inbox.heloHostname.description": "The hostname to use in the HELO/EHLO command. If not set, defaults to localhost.",
   "admin.inbox.skipTLSVerification": "Skip TLS Verification",
   "admin.inbox.skipTLSVerification.description": "Skip hostname check on the TLS certificate.",
+  "admin.inbox.enablePlusAddressing": "Enable plus addressing",
+  "admin.inbox.enablePlusAddressing.description": "Improves conversation threading but requires provider support (e.g., Gmail, Microsoft 365).",
   "admin.inbox.chooseChannel": "Choose a channel",
   "admin.inbox.configureChannel": "Configure channel",
   "admin.inbox.createEmailInbox": "Create Email Inbox",
diff --git a/internal/inbox/channel/email/email.go b/internal/inbox/channel/email/email.go
index 53eed3ce..8b437aa3 100644
--- a/internal/inbox/channel/email/email.go
+++ b/internal/inbox/channel/email/email.go
@@ -33,6 +33,7 @@ type Email struct {
 	headers              map[string]string
 	lo                   *logf.Logger
 	from                 string
+	enablePlusAddressing bool
 	messageStore         inbox.MessageStore
 	userStore            inbox.UserStore
 	wg                   sync.WaitGroup
@@ -77,6 +78,7 @@ func New(store inbox.MessageStore, userStore inbox.UserStore, opts Opts) (*Email
 		userStore:            userStore,
 		oauth:                opts.Config.OAuth,
 		authType:             opts.Config.AuthType,
+		enablePlusAddressing: opts.Config.EnablePlusAddressing,
 		tokenRefreshCallback: opts.TokenRefreshCallback,
 	}
 	return e, nil
@@ -124,11 +126,12 @@ func (e *Email) getCurrentConfig() models.Config {
 	e.oauthMu.RUnlock()
 
 	return models.Config{
-		SMTP:     e.smtpCfg,
-		IMAP:     e.imapCfg,
-		From:     e.from,
-		OAuth:    oauth,
-		AuthType: e.authType,
+		SMTP:                 e.smtpCfg,
+		IMAP:                 e.imapCfg,
+		From:                 e.from,
+		OAuth:                oauth,
+		AuthType:             e.authType,
+		EnablePlusAddressing: e.enablePlusAddressing,
 	}
 }
 
diff --git a/internal/inbox/channel/email/smtp.go b/internal/inbox/channel/email/smtp.go
index 0d7b5c6a..082ecc8e 100644
--- a/internal/inbox/channel/email/smtp.go
+++ b/internal/inbox/channel/email/smtp.go
@@ -180,9 +180,9 @@ func (e *Email) Send(m models.Message) error {
 	}
 	email.Headers.Set(headerLibredeskLoopPrevention, emailAddress)
 
-	// Set Reply-To with plus-addressing for conversation matching
+	// Set Reply-To with plus-addressing for conversation matching (if enabled)
 	// e.g., support@company.com → support+conv-{uuid}@company.com
-	if m.ConversationUUID != "" {
+	if e.enablePlusAddressing && m.ConversationUUID != "" {
 		replyToAddr := buildPlusAddress(emailAddress, m.ConversationUUID)
 		email.Headers.Set("Reply-To", replyToAddr)
 		e.lo.Debug("Reply-To header set with plus-addressing", "reply_to", replyToAddr)
diff --git a/internal/inbox/inbox.go b/internal/inbox/inbox.go
index 78827c5d..933e864c 100644
--- a/internal/inbox/inbox.go
+++ b/internal/inbox/inbox.go
@@ -305,16 +305,18 @@ func (m *Manager) Update(id int, inbox imodels.Inbox) (imodels.Inbox, error) {
 	switch current.Channel {
 	case "email":
 		var currentCfg struct {
-			AuthType string                   `json:"auth_type"`
-			OAuth    map[string]string        `json:"oauth"`
-			IMAP     []map[string]interface{} `json:"imap"`
-			SMTP     []map[string]interface{} `json:"smtp"`
+			AuthType             string            `json:"auth_type"`
+			OAuth                map[string]string `json:"oauth"`
+			IMAP                 []map[string]any  `json:"imap"`
+			SMTP                 []map[string]any  `json:"smtp"`
+			EnablePlusAddressing bool              `json:"enable_plus_addressing"`
 		}
 		var updateCfg struct {
-			AuthType string                   `json:"auth_type"`
-			OAuth    map[string]string        `json:"oauth"`
-			IMAP     []map[string]interface{} `json:"imap"`
-			SMTP     []map[string]interface{} `json:"smtp"`
+			AuthType             string            `json:"auth_type"`
+			OAuth                map[string]string `json:"oauth"`
+			IMAP                 []map[string]any  `json:"imap"`
+			SMTP                 []map[string]any  `json:"smtp"`
+			EnablePlusAddressing bool              `json:"enable_plus_addressing"`
 		}
 
 		if err := json.Unmarshal(current.Config, &currentCfg); err != nil {
@@ -496,15 +498,15 @@ func (m *Manager) encryptInboxConfig(config json.RawMessage) (json.RawMessage, e
 		return config, nil
 	}
 
-	var cfg map[string]interface{}
+	var cfg map[string]any
 	if err := json.Unmarshal(config, &cfg); err != nil {
 		return nil, fmt.Errorf("unmarshalling config: %w", err)
 	}
 
 	// Encrypt SMTP passwords
-	if smtpSlice, ok := cfg["smtp"].([]interface{}); ok {
+	if smtpSlice, ok := cfg["smtp"].([]any); ok {
 		for i, smtpItem := range smtpSlice {
-			if smtpMap, ok := smtpItem.(map[string]interface{}); ok {
+			if smtpMap, ok := smtpItem.(map[string]any); ok {
 				if password, ok := smtpMap["password"].(string); ok && password != "" {
 					encrypted, err := crypto.Encrypt(password, m.encryptionKey)
 					if err != nil {
@@ -517,9 +519,9 @@ func (m *Manager) encryptInboxConfig(config json.RawMessage) (json.RawMessage, e
 	}
 
 	// Encrypt IMAP passwords
-	if imapSlice, ok := cfg["imap"].([]interface{}); ok {
+	if imapSlice, ok := cfg["imap"].([]any); ok {
 		for i, imapItem := range imapSlice {
-			if imapMap, ok := imapItem.(map[string]interface{}); ok {
+			if imapMap, ok := imapItem.(map[string]any); ok {
 				if password, ok := imapMap["password"].(string); ok && password != "" {
 					encrypted, err := crypto.Encrypt(password, m.encryptionKey)
 					if err != nil {
@@ -532,7 +534,7 @@ func (m *Manager) encryptInboxConfig(config json.RawMessage) (json.RawMessage, e
 	}
 
 	// Encrypt OAuth fields if present
-	if oauthMap, ok := cfg["oauth"].(map[string]interface{}); ok {
+	if oauthMap, ok := cfg["oauth"].(map[string]any); ok {
 		fields := []string{"client_secret", "access_token", "refresh_token"}
 		for _, fieldName := range fields {
 			if fieldValue, ok := oauthMap[fieldName].(string); ok && fieldValue != "" {
@@ -559,15 +561,15 @@ func (m *Manager) decryptInboxConfig(config json.RawMessage) (json.RawMessage, e
 		return config, nil
 	}
 
-	var cfg map[string]interface{}
+	var cfg map[string]any
 	if err := json.Unmarshal(config, &cfg); err != nil {
 		return nil, fmt.Errorf("unmarshalling config: %w", err)
 	}
 
 	// Decrypt SMTP passwords
-	if smtpSlice, ok := cfg["smtp"].([]interface{}); ok {
+	if smtpSlice, ok := cfg["smtp"].([]any); ok {
 		for i, smtpItem := range smtpSlice {
-			if smtpMap, ok := smtpItem.(map[string]interface{}); ok {
+			if smtpMap, ok := smtpItem.(map[string]any); ok {
 				if password, ok := smtpMap["password"].(string); ok && password != "" {
 					decrypted, err := crypto.Decrypt(password, m.encryptionKey)
 					if err != nil {
@@ -580,9 +582,9 @@ func (m *Manager) decryptInboxConfig(config json.RawMessage) (json.RawMessage, e
 	}
 
 	// Decrypt IMAP passwords
-	if imapSlice, ok := cfg["imap"].([]interface{}); ok {
+	if imapSlice, ok := cfg["imap"].([]any); ok {
 		for i, imapItem := range imapSlice {
-			if imapMap, ok := imapItem.(map[string]interface{}); ok {
+			if imapMap, ok := imapItem.(map[string]any); ok {
 				if password, ok := imapMap["password"].(string); ok && password != "" {
 					decrypted, err := crypto.Decrypt(password, m.encryptionKey)
 					if err != nil {
@@ -595,7 +597,7 @@ func (m *Manager) decryptInboxConfig(config json.RawMessage) (json.RawMessage, e
 	}
 
 	// Decrypt OAuth fields if present
-	if oauthMap, ok := cfg["oauth"].(map[string]interface{}); ok {
+	if oauthMap, ok := cfg["oauth"].(map[string]any); ok {
 		fields := []string{"client_secret", "access_token", "refresh_token"}
 		for _, fieldName := range fields {
 			if fieldValue, ok := oauthMap[fieldName].(string); ok && fieldValue != "" {
diff --git a/internal/inbox/models/models.go b/internal/inbox/models/models.go
index 7874dd6f..24efeb0b 100644
--- a/internal/inbox/models/models.go
+++ b/internal/inbox/models/models.go
@@ -31,11 +31,12 @@ type Inbox struct {
 
 // Config holds the email inbox configuration with multiple SMTP servers and IMAP clients.
 type Config struct {
-	AuthType string       `json:"auth_type"` // AuthTypePassword or AuthTypeOAuth2
-	OAuth    *OAuthConfig `json:"oauth"`     // OAuth config when auth_type is "oauth2"
-	SMTP     []SMTPConfig `json:"smtp"`
-	IMAP     []IMAPConfig `json:"imap"`
-	From     string       `json:"from"`
+	AuthType             string       `json:"auth_type"` // AuthTypePassword or AuthTypeOAuth2
+	OAuth                *OAuthConfig `json:"oauth"`     // OAuth config when auth_type is "oauth2"
+	SMTP                 []SMTPConfig `json:"smtp"`
+	IMAP                 []IMAPConfig `json:"imap"`
+	From                 string       `json:"from"`
+	EnablePlusAddressing bool         `json:"enable_plus_addressing"` // Enable plus-addressing in Reply-To header for conversation matching
 }
 
 // OAuthConfig holds OAuth 2.0 authentication details.
diff --git a/internal/migrations/v1.0.1.go b/internal/migrations/v1.0.1.go
new file mode 100644
index 00000000..c12ecc16
--- /dev/null
+++ b/internal/migrations/v1.0.1.go
@@ -0,0 +1,20 @@
+package migrations
+
+import (
+	"github.com/jmoiron/sqlx"
+	"github.com/knadh/koanf/v2"
+	"github.com/knadh/stuffbin"
+)
+
+// V1_0_1 updates the database schema to v1.0.1.
+func V1_0_1(db *sqlx.DB, fs stuffbin.FileSystem, ko *koanf.Koanf) error {
+	// Backfill enable_plus_addressing to true for existing email inboxes
+	// that don't have this field in their config JSON.
+	_, err := db.Exec(`
+		UPDATE inboxes
+		SET config = jsonb_set(config, '{enable_plus_addressing}', 'true'::jsonb, true)
+		WHERE channel = 'email'
+		AND NOT (config ? 'enable_plus_addressing');
+	`)
+	return err
+}