diff --git a/admin/tool/messageinbound/classes/manager.php b/admin/tool/messageinbound/classes/manager.php
index c8ef59f4169..6596aadf8fe 100644
--- a/admin/tool/messageinbound/classes/manager.php
+++ b/admin/tool/messageinbound/classes/manager.php
@@ -310,6 +310,16 @@ class manager {
         return true;
     }
 
+    /**
+     * Remove older verification failures.
+     *
+     * @return void
+     */
+    public function tidy_old_verification_failures() {
+        global $DB;
+        $DB->delete_records_select('messageinbound_messagelist', 'timecreated < :time', ['time' => time() - DAYSECS]);
+    }
+
     /**
      * Process a message and pass it through the Inbound Message handling systems.
      *
diff --git a/admin/tool/messageinbound/classes/task/cleanup_task.php b/admin/tool/messageinbound/classes/task/cleanup_task.php
index e8b1c7a1978..fc2c01d9093 100644
--- a/admin/tool/messageinbound/classes/task/cleanup_task.php
+++ b/admin/tool/messageinbound/classes/task/cleanup_task.php
@@ -49,6 +49,7 @@ class cleanup_task extends \core\task\scheduled_task {
      */
     public function execute() {
         $manager = new \tool_messageinbound\manager();
-        return $manager->tidy_old_messages();
+        $manager->tidy_old_messages();
+        $manager->tidy_old_verification_failures();
     }
 }
diff --git a/admin/tool/messageinbound/tests/manager_test.php b/admin/tool/messageinbound/tests/manager_test.php
new file mode 100644
index 00000000000..936d99636a0
--- /dev/null
+++ b/admin/tool/messageinbound/tests/manager_test.php
@@ -0,0 +1,97 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle 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 Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Manager tests.
+ *
+ * @package    tool_messageinbound
+ * @category   test
+ * @copyright  2018 Frédéric Massart
+ * @author     Frédéric Massart <fred@branchup.tech>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+global $CFG;
+
+use core_privacy\tests\provider_testcase;
+use core_privacy\local\request\approved_contextlist;
+use core_privacy\local\request\transform;
+use core_privacy\local\request\writer;
+use tool_messageinbound\privacy\provider;
+
+/**
+ * Manager testcase class.
+ *
+ * @package    tool_messageinbound
+ * @category   test
+ * @copyright  2018 Frédéric Massart
+ * @author     Frédéric Massart <fred@branchup.tech>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class tool_messageinbound_manager_testcase extends provider_testcase {
+
+    public function setUp() {
+        global $CFG;
+        $this->resetAfterTest();
+
+        // Pretend the system is enabled.
+        $CFG->messageinbound_enabled = true;
+        $CFG->messageinbound_mailbox = 'mailbox';
+        $CFG->messageinbound_domain = 'example.com';
+    }
+
+    public function test_tidy_old_verification_failures() {
+        global $DB;
+
+        $now = time();
+        $stale = time() - DAYSECS;
+
+        $this->create_messagelist(['timecreated' => $now]);
+        $this->create_messagelist(['timecreated' => $now - HOURSECS]);
+        $this->create_messagelist(['timecreated' => $stale]);
+        $this->create_messagelist(['timecreated' => $stale - HOURSECS]);
+        $this->create_messagelist(['timecreated' => $stale - YEARSECS]);
+
+        $this->assertEquals(5, $DB->count_records('messageinbound_messagelist', []));
+        $this->assertEquals(3, $DB->count_records_select('messageinbound_messagelist', 'timecreated < :t', ['t' => $stale + 1]));
+
+        $manager = new \tool_messageinbound\manager();
+        $manager->tidy_old_verification_failures();
+
+        $this->assertEquals(2, $DB->count_records('messageinbound_messagelist', []));
+        $this->assertEquals(0, $DB->count_records_select('messageinbound_messagelist', 'timecreated < :t', ['t' => $stale + 1]));
+    }
+
+    /**
+     * Create a message to validate.
+     *
+     * @param array $params The params.
+     * @return stdClass
+     */
+    protected function create_messagelist(array $params) {
+        global $DB, $USER;
+        $record = (object) array_merge([
+            'messageid' => 'abc',
+            'userid' => $USER->id,
+            'address' => 'text@example.com',
+            'timecreated' => time(),
+        ], $params);
+        $record->id = $DB->insert_record('messageinbound_messagelist', $record);
+        return $record;
+    }
+
+}