diff --git a/plugins/bc-mail/src/Model/Table/MailFieldsTable.php b/plugins/bc-mail/src/Model/Table/MailFieldsTable.php
index 0517cb85ea..bf2013ad25 100755
--- a/plugins/bc-mail/src/Model/Table/MailFieldsTable.php
+++ b/plugins/bc-mail/src/Model/Table/MailFieldsTable.php
@@ -58,6 +58,7 @@ public function initialize(array $config): void
      */
     public function validationDefault(Validator $validator): Validator
     {
+        $validator->setProvider('bc', 'BaserCore\Model\Validation\BcValidation');
         $validator
             ->integer('id')
             ->allowEmptyString('id', null, 'create');
@@ -80,6 +81,12 @@ public function validationDefault(Validator $validator): Validator
                     'rule' => 'duplicateMailField',
                     'provider' => 'table',
                     'message' => __d('baser_core', '既に登録のあるフィールド名です。')
+                ]])
+            ->add('field_name', [
+                'reserved' => [
+                    'rule' => ['reserved'],
+                    'provider' => 'bc',
+                    'message' => __d('baser_core', 'システム予約名称のため利用できません。')
                 ]]);
         $validator
             ->scalar('type')
diff --git a/plugins/bc-mail/tests/TestCase/Model/Table/MailFieldsTableTest.php b/plugins/bc-mail/tests/TestCase/Model/Table/MailFieldsTableTest.php
index 0950579a5a..e8b9d1e933 100755
--- a/plugins/bc-mail/tests/TestCase/Model/Table/MailFieldsTableTest.php
+++ b/plugins/bc-mail/tests/TestCase/Model/Table/MailFieldsTableTest.php
@@ -158,6 +158,35 @@ public function test_validationDefaultDuplicate()
         $this->assertEquals('既に登録のあるフィールド名です。', current($errors['field_name']));
     }
 
+    /**
+     * test validationDefault reserved word check
+     * @dataProvider validationDefaultReservedDataProvider
+     */
+    public function test_validationDefaultReserved($fieldName, $expected)
+    {
+        $validator = $this->MailFieldsTable->getValidator('default');
+        $errors = $validator->validate([
+            'mail_content_id' => 999,
+            'field_name' => $fieldName,
+        ]);
+        if ($expected) {
+            $this->assertArrayNotHasKey('reserved', $errors['field_name'] ?? []);
+        } else {
+            $this->assertArrayHasKey('reserved', $errors['field_name']);
+            $this->assertEquals('システム予約名称のため利用できません。', $errors['field_name']['reserved']);
+        }
+    }
+
+    public static function validationDefaultReservedDataProvider()
+    {
+        return [
+            ['test_field', true],
+            ['select', false],
+            ['insert', false],
+            ['update', false],
+        ];
+    }
+
     /**
      * コントロールソースを取得する
      */