diff --git a/modules/oe_theme_helper/config/install/oe_theme_helper.internal_domains.yml b/modules/oe_theme_helper/config/install/oe_theme_helper.internal_domains.yml
new file mode 100644
index 0000000000..cb0c2c473a
--- /dev/null
+++ b/modules/oe_theme_helper/config/install/oe_theme_helper.internal_domains.yml
@@ -0,0 +1 @@
+internal_domain: ''
diff --git a/modules/oe_theme_helper/config/schema/oe_theme_helper.schema.yml b/modules/oe_theme_helper/config/schema/oe_theme_helper.schema.yml
index 46ea42c255..4ea6ee806d 100644
--- a/modules/oe_theme_helper/config/schema/oe_theme_helper.schema.yml
+++ b/modules/oe_theme_helper/config/schema/oe_theme_helper.schema.yml
@@ -111,3 +111,10 @@ condition.plugin.oe_theme_helper_current_component_library:
   mapping:
     component_library:
       type: string
+
+oe_theme_helper.internal_domains:
+  type: config_object
+  mapping:
+    internal_domain:
+      type: string
+      label: 'Regular expression to identify internal domains.'
diff --git a/modules/oe_theme_helper/oe_theme_helper.services.yml b/modules/oe_theme_helper/oe_theme_helper.services.yml
index 8259407aae..9f990d6b99 100644
--- a/modules/oe_theme_helper/oe_theme_helper.services.yml
+++ b/modules/oe_theme_helper/oe_theme_helper.services.yml
@@ -28,7 +28,7 @@ services:
     parent: default_plugin_manager
   oe_theme_helper.twig_extension.twig_extension:
     class: Drupal\oe_theme_helper\TwigExtension\TwigExtension
-    arguments: ['@language_manager', '@renderer']
+    arguments: ['@language_manager', '@renderer', '@oe_theme_helper.external_links']
     tags:
     - { name: twig.extension }
   oe_theme_helper.node_metadata_event_subscriber:
@@ -42,3 +42,4 @@ services:
     arguments: ['@entity_type.bundle.info']
   oe_theme_helper.external_links:
     class: Drupal\oe_theme_helper\ExternalLinks
+    arguments: ['@config.factory']
diff --git a/modules/oe_theme_helper/src/ExternalLinks.php b/modules/oe_theme_helper/src/ExternalLinks.php
index 3b8c316807..77e5752488 100644
--- a/modules/oe_theme_helper/src/ExternalLinks.php
+++ b/modules/oe_theme_helper/src/ExternalLinks.php
@@ -5,6 +5,7 @@
 namespace Drupal\oe_theme_helper;
 
 use Drupal\Component\Utility\UrlHelper;
+use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Url;
 
 /**
@@ -12,6 +13,23 @@
  */
 class ExternalLinks implements ExternalLinksInterface {
 
+  /**
+   * The configuration factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactoryInterface
+   */
+  protected $configFactory;
+
+  /**
+   * Constructs an ExternalLinks object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The configuration factory.
+   */
+  public function __construct(ConfigFactoryInterface $config_factory) {
+    $this->configFactory = $config_factory;
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -28,28 +46,12 @@ public function isExternalLink($url): bool {
       return $external;
     }
 
-    // If it's external link, make sure its domain is not considered internal.
-    $internal_domains = $this->internalDomains();
-    foreach ($internal_domains as $internal_domain) {
-      if (strpos($path, $internal_domain)) {
-        $external = FALSE;
-        break;
-      }
+    // If it's an external link, make sure its domain is not internal.
+    $internal_domain_expression = $this->configFactory->get('oe_theme_helper.internal_domains')->get('internal_domain');
+    if (!$internal_domain_expression) {
+      return $external;
     }
-
-    return $external;
-  }
-
-  /**
-   * Defines a list of domain considered internal.
-   *
-   * @return array|null
-   *   The list of internal domains or NULL if there is none.
-   */
-  protected function internalDomains(): ?array {
-    return [
-      'europa.eu',
-    ];
+    return !preg_match_all($internal_domain_expression, $path);
   }
 
 }
diff --git a/modules/oe_theme_helper/src/TwigExtension/TwigExtension.php b/modules/oe_theme_helper/src/TwigExtension/TwigExtension.php
index 698cd4cd36..da01d999a1 100644
--- a/modules/oe_theme_helper/src/TwigExtension/TwigExtension.php
+++ b/modules/oe_theme_helper/src/TwigExtension/TwigExtension.php
@@ -16,6 +16,7 @@
 use Drupal\Core\Render\RendererInterface;
 use Drupal\Core\Template\Attribute;
 use Drupal\oe_theme_helper\EuropeanUnionLanguages;
+use Drupal\oe_theme_helper\ExternalLinksInterface;
 use Drupal\smart_trim\Truncate\TruncateHTML;
 use Drupal\Core\Template\TwigExtension as CoreTwigExtension;
 use Twig\Environment;
@@ -45,6 +46,13 @@ class TwigExtension extends AbstractExtension {
    */
   protected $renderer;
 
+  /**
+   * The external links service.
+   *
+   * @var \Drupal\oe_theme_helper\ExternalLinksInterface
+   */
+  protected $externalLinks;
+
   /**
    * Constructs a new TwigExtension object.
    *
@@ -52,10 +60,13 @@ class TwigExtension extends AbstractExtension {
    *   The language manager.
    * @param \Drupal\Core\Render\RendererInterface $renderer
    *   The renderer service.
+   * @param \Drupal\oe_theme_helper\ExternalLinksInterface $external_links
+   *   The external links service.
    */
-  public function __construct(LanguageManagerInterface $languageManager, RendererInterface $renderer) {
+  public function __construct(LanguageManagerInterface $languageManager, RendererInterface $renderer, ExternalLinksInterface $external_links) {
     $this->languageManager = $languageManager;
     $this->renderer = $renderer;
+    $this->externalLinks = $external_links;
   }
 
   /**
@@ -535,7 +546,7 @@ public function getLinkIcon(array $context, string $path, string $size = 's'): a
       'size' => $size,
       'color' => 'primary',
     ];
-    if (\Drupal::service('oe_theme_helper.external_links')->isExternalLink($path)) {
+    if ($this->externalLinks->isExternalLink($path)) {
       $icon['name'] = 'external';
     }
     else {
diff --git a/tests/src/Kernel/AbstractKernelTestBase.php b/tests/src/Kernel/AbstractKernelTestBase.php
index 8b7ef87e0b..063dc47921 100644
--- a/tests/src/Kernel/AbstractKernelTestBase.php
+++ b/tests/src/Kernel/AbstractKernelTestBase.php
@@ -52,6 +52,7 @@ protected function setUp(): void {
     $this->container->get('theme_installer')->install(['oe_theme']);
     $this->config('system.theme')->set('default', 'oe_theme')->save();
     $this->container->set('theme.registry', NULL);
+    $this->config('oe_theme_helper.internal_domains')->set('internal_domain', '/(^|^[^:]+:\/\/|[^\.]+\.)europa\.eu/m')->save();
 
     // @todo Drupal 9 ignores settings in settings.testing.php in kernel tests.
     // See https://www.drupal.org/project/drupal/issues/3190974. Need to