diff --git a/integration_test/scenarios/labels/remove_a_label_from_email_scenario.dart b/integration_test/scenarios/labels/remove_a_label_from_email_scenario.dart
index 9d00e0e67..8f36c0d7e 100644
--- a/integration_test/scenarios/labels/remove_a_label_from_email_scenario.dart
+++ b/integration_test/scenarios/labels/remove_a_label_from_email_scenario.dart
@@ -19,6 +19,7 @@ class RemoveALabelFromEmailScenario extends BaseTestScenario
   @override
   Future<void> runTestLogic() async {
     const emailUser = String.fromEnvironment('BASIC_AUTH_EMAIL');
+    expect(emailUser, isNotEmpty, reason: 'BASIC_AUTH_EMAIL must be set');
 
     final threadRobot = ThreadRobot($);
     final emailRobot = EmailRobot($);
diff --git a/lib/features/email/data/network/email_api.dart b/lib/features/email/data/network/email_api.dart
index 2abb44e32..7ef5187d2 100644
--- a/lib/features/email/data/network/email_api.dart
+++ b/lib/features/email/data/network/email_api.dart
@@ -971,6 +971,10 @@ class EmailAPI with HandleSetErrorMixin, MailAPIMixin {
     List<EmailId> emailIds,
     KeyWordIdentifier labelKeyword,
   ) async {
+    if (emailIds.isEmpty) {
+      throw ArgumentError.value(emailIds, 'emailIds', 'must not be empty');
+    }
+
     final method = SetEmailMethod(accountId)
       ..addUpdates(emailIds.generateMapUpdateObjectLabel(labelKeyword));
 
@@ -987,8 +991,9 @@ class EmailAPI with HandleSetErrorMixin, MailAPIMixin {
     );
 
     final emailIdsUpdated = response?.updated?.keys ?? <Id>[];
-    final ids = emailIds.map((emailId) => emailId.id);
-    final isUpdated = emailIdsUpdated.every(ids.contains);
+    final ids = emailIds.toSetIds();
+    final isUpdated = ids.every(emailIdsUpdated.contains) &&
+        emailIdsUpdated.length == ids.length;
 
     if (emailIdsUpdated.isEmpty || !isUpdated) {
       throw parseErrorForSetResponse(response, emailIds.first.id);
@@ -1031,6 +1036,10 @@ class EmailAPI with HandleSetErrorMixin, MailAPIMixin {
     List<EmailId> emailIds,
     KeyWordIdentifier labelKeyword,
   ) async {
+    if (emailIds.isEmpty) {
+      throw ArgumentError.value(emailIds, 'emailIds', 'must not be empty');
+    }
+
     final method = SetEmailMethod(accountId)
       ..addUpdates(emailIds.generateMapUpdateObjectLabel(
         labelKeyword,
@@ -1050,13 +1059,12 @@ class EmailAPI with HandleSetErrorMixin, MailAPIMixin {
     );
 
     final emailIdsUpdated = response?.updated?.keys ?? <Id>[];
-    final ids = emailIds.map((emailId) => emailId.id);
-    final isUpdated = emailIdsUpdated.every(ids.contains);
+    final ids = emailIds.toSetIds();
+    final isUpdated = emailIdsUpdated.every(ids.contains) &&
+        emailIdsUpdated.length == ids.length;
 
     if (emailIdsUpdated.isEmpty || !isUpdated) {
-      for (var id in emailIds) {
-        throw parseErrorForSetResponse(response, id.id);
-      }
+      throw parseErrorForSetResponse(response, emailIds.first.id);
     }
   }
 }
\ No newline at end of file
diff --git a/lib/features/thread/data/extensions/map_keywords_extension.dart b/lib/features/thread/data/extensions/map_keywords_extension.dart
index 26d7a1e54..2990cae09 100644
--- a/lib/features/thread/data/extensions/map_keywords_extension.dart
+++ b/lib/features/thread/data/extensions/map_keywords_extension.dart
@@ -32,11 +32,11 @@ extension MapKeywordsExtension on Map<KeyWordIdentifier, bool>? {
     this?.remove(keyword);
   }
 
-  void toggleKeyword(KeyWordIdentifier keyword, bool remove) {
-    if (remove) {
-      this?.remove(keyword);
+  void toggleKeyword(KeyWordIdentifier keyword, bool shouldRemove) {
+    if (shouldRemove) {
+      removeKeyword(keyword);
     } else {
-      this?[keyword] = true;
+      addKeyword(keyword);
     }
   }
 }
diff --git a/model/lib/extensions/list_email_id_extension.dart b/model/lib/extensions/list_email_id_extension.dart
index 0ea686fbf..962049188 100644
--- a/model/lib/extensions/list_email_id_extension.dart
+++ b/model/lib/extensions/list_email_id_extension.dart
@@ -9,6 +9,8 @@ extension ListEmailIdExtension on List<EmailId> {
 
   List<Id> toIds() => map((emailId) => emailId.id).toList();
 
+  Set<Id> toSetIds() => map((emailId) => emailId.id).toSet();
+
   Map<Id, PatchObject> generateMapUpdateObjectMarkAsRead(ReadActions readActions) {
     return {
       for (var emailId in this)