diff --git a/inmail.drush.inc b/inmail.drush.inc
index 9932620..80434b1 100644
--- a/inmail.drush.inc
+++ b/inmail.drush.inc
@@ -70,6 +70,10 @@ function drush_inmail_process() {
     drush_set_error(dt('Deliverer "@deliverer_id" not found', ['@deliverer_id' => $deliverer_config_id]));
     return;
   }
+  if (!$deliverer->isAvailable()) {
+    drush_set_error(dt('Deliverer "@deliverer_id" is not available', ['@deliverer_id' => $deliverer_config_id]));
+    return;
+  }
 
   if (count($args) > 0) {
     $raws = array();
diff --git a/inmail.install b/inmail.install
index 61a4396..aa33b32 100644
--- a/inmail.install
+++ b/inmail.install
@@ -10,38 +10,48 @@
 function inmail_requirements($phase) {
   $requirements = [];
   if ($phase == 'runtime') {
-    $requirements += inmail_get_plugin_requirements();
+    $requirements += inmail_get_requirements();
   }
 
   return $requirements;
 }
 
 /**
- * Returns plugin requirements for enabled instances.
+ * Returns plugin and instance requirements.
  *
  * @return array
- *   An array of plugin requirements.
+ *   An array of plugin and instance requirements.
  */
-function inmail_get_plugin_requirements() {
+function inmail_get_requirements() {
   /** @var \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager */
   $entity_type_manager = \Drupal::entityTypeManager();
-  $plugin_types = ['analyzer', 'deliverer', 'handler'];
-  $plugin_requirements = [];
+  $plugin_types = [
+    'analyzer' =>  \Drupal::service('plugin.manager.inmail.analyzer'),
+    'deliverer' => \Drupal::service('plugin.manager.inmail.deliverer'),
+    'handler' => \Drupal::service('plugin.manager.inmail.handler'),
+  ];
+  $requirements = [];
+
+  /** @var Drupal\Core\Plugin\DefaultPluginManager $plugin_manager */
+  foreach ($plugin_types as $plugin_type => $plugin_manager) {
+    // Check plugin requirements for the current plugin type.
+    foreach ($plugin_manager->getDefinitions() as $plugin_id => $definition) {
+      $plugin_instance = $plugin_manager->createInstance($plugin_id);
+      $requirements[$plugin_type . '_plugin_' . $plugin_id] = $plugin_instance->checkPluginRequirements();
+    }
 
-  foreach ($plugin_types as $plugin_type) {
+    // Check instance requirements.
     $enabled_instances = $entity_type_manager->getStorage("inmail_$plugin_type")->loadByProperties(['status' => TRUE]);
     /** @var \Drupal\inmail\Entity\PluginConfigEntity $enabled_instance */
     foreach ($enabled_instances as $enabled_instance) {
-      if (!$enabled_instance->isAvailable()) {
-        $key = $plugin_type . '_' . $enabled_instance->getPluginId();
-        if (!isset($plugin_requirements[$key])) {
-          $plugin_requirements[$key] = $enabled_instance->checkRequirements();
-        }
-      }
+      $requirements[$plugin_type . '_config_' . $enabled_instance->id()] = $enabled_instance->checkInstanceRequirements();
     }
   }
 
-  return $plugin_requirements;
+  // Filter plugins/instances with no requirements.
+  $requirements = array_filter($requirements);
+
+  return $requirements;
 }
 
 /**
diff --git a/inmail_demo/src/Form/PasteForm.php b/inmail_demo/src/Form/PasteForm.php
index 26d3368..fe541c4 100644
--- a/inmail_demo/src/Form/PasteForm.php
+++ b/inmail_demo/src/Form/PasteForm.php
@@ -187,17 +187,20 @@ class PasteForm extends FormBase {
   }
 
   /**
-   * Loads and returns all deliverer configs using the Paste deliverer.
+   * Loads and returns all available deliverer configs using Paste deliverer.
    *
    * @return \Drupal\inmail\Entity\DelivererConfig[]
-   *   All enabled Paste deliverer configs.
+   *   All enabled and available Paste deliverer configs.
    */
   protected function getDelivererConfigs() {
     $ids = $this->delivererStorage->getQuery()
       ->condition('plugin', 'paste')
       ->condition('status', TRUE)
       ->execute();
-    return $this->delivererStorage->loadMultiple($ids);
+    $deliverers = $this->delivererStorage->loadMultiple($ids);
+    return array_filter($deliverers, function ($deliverer) {
+      return $deliverer->isAvailable();
+    });
   }
 
   /**
diff --git a/src/Entity/PluginConfigEntity.php b/src/Entity/PluginConfigEntity.php
index f704a3d..2ccb1fd 100644
--- a/src/Entity/PluginConfigEntity.php
+++ b/src/Entity/PluginConfigEntity.php
@@ -114,11 +114,25 @@ abstract class PluginConfigEntity extends ConfigEntityBase implements PluginRequ
   /**
    * {@inheritdoc}
    */
-  public function checkRequirements() {
+  public function checkPluginRequirements() {
     $requirements = [];
 
     if ($plugin = $this->getPluginInstance()) {
-      return $plugin->checkRequirements();
+      return $plugin->checkPluginRequirements();
+    }
+
+    return $requirements;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function checkInstanceRequirements() {
+    // Add title.
+    $requirements['title'] = $this->label();
+
+    if ($plugin = $this->getPluginInstance()) {
+      $requirements += $plugin->checkInstanceRequirements();
     }
 
     return $requirements;
diff --git a/src/Form/DelivererListForm.php b/src/Form/DelivererListForm.php
index ab84e80..ecde679 100644
--- a/src/Form/DelivererListForm.php
+++ b/src/Form/DelivererListForm.php
@@ -77,7 +77,7 @@ class DelivererListForm extends FormBase {
       // Get plugin instance.
       $deliverer = $this->delivererManager->createInstance($deliverer_config->getPluginId(), $deliverer_config->getConfiguration());
       // Update plugin.
-      if ($deliverer instanceof FetcherInterface) {
+      if ($deliverer instanceof FetcherInterface && $deliverer->isAvailable()) {
         $deliverer->update();
         $deliverer->setLastCheckedTime(REQUEST_TIME);
         $fetchers_count++;
diff --git a/src/PluginBase.php b/src/PluginBase.php
index a5914e3..5bdfa4e 100644
--- a/src/PluginBase.php
+++ b/src/PluginBase.php
@@ -12,7 +12,14 @@ abstract class PluginBase extends CorePluginBase implements PluginRequirementsIn
   /**
    * {@inheritdoc}
    */
-  public function checkRequirements() {
+  public function checkPluginRequirements() {
+    return [];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function checkInstanceRequirements() {
     return [];
   }
 
diff --git a/src/PluginRequirementsInterface.php b/src/PluginRequirementsInterface.php
index 052bcf4..114ead6 100644
--- a/src/PluginRequirementsInterface.php
+++ b/src/PluginRequirementsInterface.php
@@ -14,7 +14,16 @@ interface PluginRequirementsInterface {
    *   Returns the structured verbose output if requirements are not met.
    *   In case of no plugin requirements, an empty array is returned.
    */
-  public function checkRequirements();
+  public function checkPluginRequirements();
+
+  /**
+   * Checks requirements of the current configuration instance.
+   *
+   * @return array
+   *   Returns the structured verbose output if requirements are not met.
+   *   In case of no instance requirements, an empty array is returned.
+   */
+  public function checkInstanceRequirements();
 
   /**
    * Flag determining whether a plugin is available to be used in processing.
diff --git a/tests/modules/inmail_test/src/Plugin/inmail/Analyzer/UnavailableAnalyzer.php b/tests/modules/inmail_test/src/Plugin/inmail/Analyzer/UnavailableAnalyzer.php
index 9076853..9c275a0 100644
--- a/tests/modules/inmail_test/src/Plugin/inmail/Analyzer/UnavailableAnalyzer.php
+++ b/tests/modules/inmail_test/src/Plugin/inmail/Analyzer/UnavailableAnalyzer.php
@@ -32,7 +32,7 @@ class UnavailableAnalyzer extends AnalyzerBase {
   /**
    * {@inheritdoc}
    */
-  public function checkRequirements() {
+  public function checkPluginRequirements() {
     return [
       'title' => $this->t('Unavailable Analyzer'),
       'description' => $this->t('Unavailable Analyzer cannot be used.'),
@@ -43,6 +43,16 @@ class UnavailableAnalyzer extends AnalyzerBase {
   /**
    * {@inheritdoc}
    */
+  public function checkInstanceRequirements() {
+    return [
+      'description' => $this->t('Wrong instance configuration.'),
+      'severity' => REQUIREMENT_ERROR,
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function isAvailable() {
     return FALSE;
   }
diff --git a/tests/src/Kernel/ProcessorTest.php b/tests/src/Kernel/ProcessorTest.php
index f385fb1..0c4ea2e 100644
--- a/tests/src/Kernel/ProcessorTest.php
+++ b/tests/src/Kernel/ProcessorTest.php
@@ -63,7 +63,11 @@ EOF;
 
     AnalyzerConfig::create(['id' => 'test_analyzer', 'plugin' => 'test_analyzer'])->save();
     // Add an unavailable analyzer.
-    $unavailable_analyzer = AnalyzerConfig::create(['id' => 'unavailable_analyzer', 'plugin' => 'unavailable_analyzer']);
+    $unavailable_analyzer = AnalyzerConfig::create([
+      'id' => 'unavailable_analyzer',
+      'label' => 'Unavailable Analyzer',
+      'plugin' => 'unavailable_analyzer',
+    ]);
     $unavailable_analyzer->save();
 
     HandlerConfig::create(['id' => 'result_keeper', 'plugin' => 'result_keeper'])->save();
@@ -78,12 +82,17 @@ EOF;
     // Assert the account was switched on handler's level.
     $this->assertEquals('Demo User', ResultKeeperHandler::getAccountName());
 
-    // Assert the requirements message.
+    // Assert the requirements messages.
     $this->assertEquals([
       'title' => t('Unavailable Analyzer'),
       'description' => t('Unavailable Analyzer cannot be used.'),
       'severity' => REQUIREMENT_ERROR,
-    ], $unavailable_analyzer->checkRequirements());
+    ], $unavailable_analyzer->checkPluginRequirements());
+    $this->assertEquals([
+      'title' => t('Unavailable Analyzer'),
+      'description' => t('Wrong instance configuration.'),
+      'severity' => REQUIREMENT_ERROR,
+    ], $unavailable_analyzer->checkInstanceRequirements());
     $this->assertEquals(FALSE, $unavailable_analyzer->isAvailable());
     // The body message has not changed. It implies UnavailableAnalyzer
     // did not run.