diff --git a/inmail_monitoring/config/schema/inmail_monitoring.schema.yml b/inmail_monitoring/config/schema/inmail_monitoring.schema.yml
new file mode 100644
index 0000000..e7e3eac
--- /dev/null
+++ b/inmail_monitoring/config/schema/inmail_monitoring.schema.yml
@@ -0,0 +1,8 @@
+# Schema for IMAP quota sensor.
+monitoring.settings.inmail_monitoring_imap_quota:
+  type: monitoring.settings_base
+  label: 'IMAP quota sensor settings'
+  mapping:
+    imap_fetcher:
+      label: Inmail IMAP fetcher to track its quota
+      type: string
diff --git a/inmail_monitoring/inmail_monitoring.info.yml b/inmail_monitoring/inmail_monitoring.info.yml
new file mode 100644
index 0000000..a988931
--- /dev/null
+++ b/inmail_monitoring/inmail_monitoring.info.yml
@@ -0,0 +1,10 @@
+name: Inmail Monitoring
+type: module
+description: Monitors the state of Inmail module.
+package: Mail
+version: 8.x-1.x
+core: 8.x
+
+dependencies:
+  - inmail
+  - monitoring
diff --git a/inmail_monitoring/src/Plugin/monitoring/SensorPlugin/IMAPQuotaSensorPlugin.php b/inmail_monitoring/src/Plugin/monitoring/SensorPlugin/IMAPQuotaSensorPlugin.php
new file mode 100644
index 0000000..1b3260e
--- /dev/null
+++ b/inmail_monitoring/src/Plugin/monitoring/SensorPlugin/IMAPQuotaSensorPlugin.php
@@ -0,0 +1,95 @@
+<?php
+
+namespace Drupal\inmail_monitoring\Plugin\monitoring\SensorPlugin;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\inmail\Entity\DelivererConfig;
+use Drupal\inmail\Plugin\inmail\Deliverer\ImapFetcher;
+use Drupal\monitoring\Result\SensorResultInterface;
+use Drupal\monitoring\SensorPlugin\SensorPluginBase;
+
+/**
+ * Monitors IMAP quota of Inmail fetchers.
+ *
+ * @SensorPlugin(
+ *   id = "inmail_monitoring_imap_quota",
+ *   label = @Translation("Inmail IMAP Quota"),
+ *   description = @Translation("Monitors IMAP quota of Inmail fetchers."),
+ *   addable = FALSE
+ * )
+ */
+class IMAPQuotaSensorPlugin extends SensorPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
+    $form = parent::buildConfigurationForm($form, $form_state);
+
+    // Find active deliverers.
+    $deliverer_ids = \Drupal::entityQuery('inmail_deliverer')->condition('status', TRUE)->execute();
+    /** @var \Drupal\inmail\Entity\DelivererConfig[] $deliverers */
+    $deliverers = \Drupal::entityTypeManager()->getStorage('inmail_deliverer')->loadMultiple($deliverer_ids);
+    /** @var \Drupal\Component\Plugin\PluginManagerInterface $deliverer_manager */
+    $deliverer_manager = \Drupal::service('plugin.manager.inmail.deliverer');
+
+    $imap_fetchers = [];
+    foreach ($deliverers as $deliverer) {
+      // @todo: Replace with getPluginInstance() after https://www.drupal.org/node/2769617.
+      $plugin = $deliverer_manager->createInstance($deliverer->getPluginId(), $deliverer->getConfiguration());
+
+      // List IMAP fetchers only.
+      if ($plugin instanceof ImapFetcher) {
+        $imap_fetchers[$deliverer->id()] = $deliverer->label();
+      }
+    }
+
+    $form['imap_fetcher'] = array(
+      '#type' => 'radios',
+      '#options' => $imap_fetchers,
+      '#title' => t('IMAP Fetchers'),
+      '#description' => t('Select a fetcher to track its IMAP quota.'),
+      '#default_value' => $this->sensorConfig->getSetting('imap_fetcher'),
+    );
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
+    $sensor_config = $form_state->getFormObject()->getEntity();
+    parent::submitConfigurationForm($form, $form_state);
+
+    $sensor_config->settings['imap_fetcher'] = $form_state->getValue(['settings', 'imap_fetcher']);
+  }
+
+    /**
+   * {@inheritdoc}
+   */
+  public function runSensor(SensorResultInterface $result) {
+    $imap_fetcher = DelivererConfig::load($this->sensorConfig->settings['imap_fetcher']);
+    // @todo: Replace with getPluginInstance() after https://www.drupal.org/node/2769617.
+    /** @var \Drupal\Component\Plugin\PluginManagerInterface $deliverer_manager */
+    $deliverer_manager = \Drupal::service('plugin.manager.inmail.deliverer');
+    $plugin = $deliverer_manager->createInstance($imap_fetcher->getPluginId(), $imap_fetcher->getConfiguration());
+
+    if ($quota = $plugin->getQuota()) {
+      $usage = $quota['STORAGE']['usage'];
+      $limit = $quota['STORAGE']['limit'];
+      if ($usage >= $limit) {
+        $result->setStatus(SensorResultInterface::STATUS_CRITICAL);
+      }
+      else {
+        $result->setStatus(SensorResultInterface::STATUS_OK);
+      }
+      $result->setValue($usage);
+      $result->setMessage('The usage quota for @imap_fetcher is @usage KB and the limit is @limit KB', ['@imap_fetcher' => $imap_fetcher->id(), '@usage' => $usage, '@limit' => $limit]);
+    }
+    else {
+      $result->setStatus(SensorResultInterface::STATUS_UNKNOWN);
+      $result->setMessage('No quota information for @imap_fetcher fetcher.', ['@imap_fetcher' => $imap_fetcher->id()]);
+    }
+  }
+}
diff --git a/src/Plugin/inmail/Deliverer/FetcherInterface.php b/src/Plugin/inmail/Deliverer/FetcherInterface.php
index 26b0bcd..4e28228 100644
--- a/src/Plugin/inmail/Deliverer/FetcherInterface.php
+++ b/src/Plugin/inmail/Deliverer/FetcherInterface.php
@@ -38,6 +38,14 @@ interface FetcherInterface extends DelivererInterface, ConfigurablePluginInterfa
   public function update();
 
   /**
+   * Retrieves the quota settings for "INBOX".
+   *
+   * @return array|null
+   *    An array of usage and limit or null if quota is not available.
+   */
+  public function getQuota();
+
+  /**
    * Update the timestamp of the last status check made.
    *
    * @param int|null $timestamp
diff --git a/src/Plugin/inmail/Deliverer/ImapFetcher.php b/src/Plugin/inmail/Deliverer/ImapFetcher.php
index 71dc8c3..7bcdcbd 100644
--- a/src/Plugin/inmail/Deliverer/ImapFetcher.php
+++ b/src/Plugin/inmail/Deliverer/ImapFetcher.php
@@ -92,6 +92,19 @@ class ImapFetcher extends FetcherBase implements ContainerFactoryPluginInterface
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function getQuota() {
+    return $this->doImap(function($imap_stream) {
+      $quota = imap_get_quotaroot($imap_stream, 'INBOX');
+      if (!empty($quota) && is_array($quota)) {
+        return $quota;
+      }
+      return NULL;
+    });
+  }
+
+  /**
    * Connect to IMAP server and perform arbitrary operations.
    *
    * If connection fails, an exception is thrown and the callback is never