diff --git a/apigee_edge.module b/apigee_edge.module
index f0a0a18c..6a542c39 100644
--- a/apigee_edge.module
+++ b/apigee_edge.module
@@ -326,6 +326,7 @@ function apigee_edge_entity_base_field_info_alter(&$fields, EntityTypeInterface
     $mail = $fields['mail'];
     $mail->setRequired(TRUE);
     $mail->addConstraint('DeveloperMailUnique');
+    $mail->addConstraint('DeveloperLowercaseEmail');
 
     // Add a bundle to these fields to allow other modules to display them
     // as configurable (fields added through the UI or configuration do have a
@@ -336,6 +337,28 @@ function apigee_edge_entity_base_field_info_alter(&$fields, EntityTypeInterface
   }
 }
 
+/**
+ * Implements hook_form_FORM_ID_alter() for install_configure_form().
+ *
+ * Allows the profile to alter the site configuration form.
+ */
+function apigee_edge_form_install_configure_form_alter(&$form, FormStateInterface $form_state) {
+  $form['#validate'][] = '_apigee_edge_site_install_form_check_email';
+}
+
+/**
+*  @internal
+*/
+function _apigee_edge_site_install_form_check_email(&$form, FormStateInterface $form_state) {
+  $org_controller = \Drupal::service('apigee_edge.controller.organization');
+  // Check if org is ApigeeX.
+  if ($org_controller->isOrganizationApigeeX()) {
+    if (preg_match('/[A-Z]/', $form_state->getValue(['account', 'mail']))) {
+      $form_state->setErrorByName('account][mail', 'This email address accepts only lowercase characters.');
+    }
+  }
+}
+
 /**
  * Implements hook_entity_extra_field_info().
  */
diff --git a/src/Plugin/Validation/Constraint/LowercaseEmailConstraint.php b/src/Plugin/Validation/Constraint/LowercaseEmailConstraint.php
new file mode 100644
index 00000000..aef5c3c8
--- /dev/null
+++ b/src/Plugin/Validation/Constraint/LowercaseEmailConstraint.php
@@ -0,0 +1,43 @@
+<?php
+
+/**
+ * Copyright 2024 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+ * USA.
+ */
+
+namespace Drupal\apigee_edge\Plugin\Validation\Constraint;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * Checks that the submitted value is a unique integer.
+ *
+ * @Constraint(
+ *   id = "DeveloperLowercaseEmail",
+ *   label = @Translation("Developer Lowercase Email", context = "Validation"),
+ *   type = "email"
+ * )
+ */
+class LowercaseEmailConstraint extends Constraint {
+
+  /**
+   * The message that will be shown if the value contains any uppercase characters.
+   *
+   * @var string
+   */
+  public $notLowercase = 'This email address accepts only lowercase characters.';
+
+}
diff --git a/src/Plugin/Validation/Constraint/LowercaseEmailConstraintValidator.php b/src/Plugin/Validation/Constraint/LowercaseEmailConstraintValidator.php
new file mode 100644
index 00000000..d195c0c9
--- /dev/null
+++ b/src/Plugin/Validation/Constraint/LowercaseEmailConstraintValidator.php
@@ -0,0 +1,103 @@
+<?php
+
+/**
+ * Copyright 2024 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+ * USA.
+ */
+
+namespace Drupal\apigee_edge\Plugin\Validation\Constraint;
+
+use Drupal\apigee_edge\Entity\Controller\OrganizationController;
+use Drupal\apigee_edge\SDKConnectorInterface;
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * Validates the LowercaseEmail constraint.
+ */
+class LowercaseEmailConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {
+
+  /**
+   * The internal entity cache.
+   *
+   * @var \Apigee\Edge\Api\Management\Entity\OrganizationInterface[]
+   */
+  private $cache = [];
+
+  /**
+   * The organization controller service.
+   *
+   * @var \Drupal\apigee_edge\Entity\Controller\OrganizationController
+   */
+  private $orgController;
+
+  /**
+   * The sdk comnector service.
+   *
+   * @var \Drupal\apigee_edge\SDKConnectorInterface
+   */
+  private $sdkConnector;
+
+  /**
+   * Constructs a ValidReferenceConstraintValidator object.
+   *
+   * @param \Drupal\apigee_edge\SDKConnectorInterface $sdk_connector
+   *   The SDK connector service.
+   * @param \Drupal\apigee_edge\Entity\Controller\OrganizationController $org_controller
+   *   The organization controller service.
+   */
+  public function __construct(SDKConnectorInterface $sdk_connector, OrganizationController $org_controller) {
+    $this->sdkConnector = $sdk_connector;
+    $this->orgController = $org_controller;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('apigee_edge.sdk_connector'),
+      $container->get('apigee_edge.controller.organization')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validate($value, Constraint $constraint) {
+    try {
+      if (!isset($this->cache[$this->sdkConnector->getOrganization()])) {
+        $this->cache[$this->sdkConnector->getOrganization()] = $this->orgController;
+      }
+      // Check if organization is ApigeeX.
+      if ($this->cache[$this->sdkConnector->getOrganization()]->isOrganizationApigeeX()) {
+        foreach ($value as $item) {
+          if (preg_match('/[A-Z]/', $item->value)) {
+            // The value contains uppercase character, the error, is applied.
+            $this->context->addViolation($constraint->notLowercase, ['%value' => $item->value]);
+          }
+        }
+      }
+    }
+    catch (\Exception $e) {
+      // If not able to connect to Apigee Edge.
+      \Drupal::logger('apigee_edge')->error($e->getMessage());
+    }
+  }
+
+}