diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index 864719a674a..5ebe7afedec 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -6436,8 +6436,10 @@ function send_password_change_info($user) {
 function email_is_not_allowed($email) {
     global $CFG;
 
+    // Comparing lowercase domains.
+    $email = strtolower($email);
     if (!empty($CFG->allowemailaddresses)) {
-        $allowed = explode(' ', $CFG->allowemailaddresses);
+        $allowed = explode(' ', strtolower($CFG->allowemailaddresses));
         foreach ($allowed as $allowedpattern) {
             $allowedpattern = trim($allowedpattern);
             if (!$allowedpattern) {
@@ -6456,7 +6458,7 @@ function email_is_not_allowed($email) {
         return get_string('emailonlyallowed', '', $CFG->allowemailaddresses);
 
     } else if (!empty($CFG->denyemailaddresses)) {
-        $denied = explode(' ', $CFG->denyemailaddresses);
+        $denied = explode(' ', strtolower($CFG->denyemailaddresses));
         foreach ($denied as $deniedpattern) {
             $deniedpattern = trim($deniedpattern);
             if (!$deniedpattern) {
diff --git a/lib/tests/moodlelib_test.php b/lib/tests/moodlelib_test.php
index 5f3eab48d97..451893f4fca 100644
--- a/lib/tests/moodlelib_test.php
+++ b/lib/tests/moodlelib_test.php
@@ -3928,6 +3928,163 @@ class core_moodlelib_testcase extends advanced_testcase {
         $this->assertTrue(validate_email(generate_email_processing_address(23, $modargs)));
     }
 
+    /**
+     * Test allowemailaddresses setting.
+     *
+     * @param string $email Email address for the from user.
+     * @param string $config The CFG->allowemailaddresses config values
+     * @param false/string $result The expected result.
+     *
+     * @dataProvider data_email_is_not_allowed_for_allowemailaddresses
+     */
+    public function test_email_is_not_allowed_for_allowemailaddresses($email, $config, $result) {
+        $this->resetAfterTest();
+
+        set_config('allowemailaddresses', $config);
+        $this->assertEquals($result, email_is_not_allowed($email));
+    }
+
+    /**
+     * Data provider for data_email_is_not_allowed_for_allowemailaddresses.
+     *
+     * @return array Returns an array of test data for the above function.
+     */
+    public function data_email_is_not_allowed_for_allowemailaddresses() {
+        return [
+            // Test allowed domain empty list.
+            [
+                'email' => 'fromuser@example.com',
+                'config' => '',
+                'result' => false
+            ],
+            // Test from email is in allowed domain.
+            [
+                'email' => 'fromuser@example.com',
+                'config' => 'example.com test.com',
+                'result' => false
+            ],
+            // Test from email is in allowed domain but uppercase config.
+            [
+                'email' => 'fromuser@example.com',
+                'config' => 'EXAMPLE.com test.com',
+                'result' => false
+            ],
+            // Test from email is in allowed domain but uppercase email.
+            [
+                'email' => 'fromuser@EXAMPLE.com',
+                'config' => 'example.com test.com',
+                'result' => false
+            ],
+            // Test from email is in allowed subdomain.
+            [
+                'email' => 'fromuser@something.example.com',
+                'config' => '.example.com test.com',
+                'result' => false
+            ],
+            // Test from email is in allowed subdomain but uppercase config.
+            [
+                'email' => 'fromuser@something.example.com',
+                'config' => '.EXAMPLE.com test.com',
+                'result' => false
+            ],
+            // Test from email is in allowed subdomain but uppercase email.
+            [
+                'email' => 'fromuser@something.EXAMPLE.com',
+                'config' => '.example.com test.com',
+                'result' => false
+            ],
+            // Test from email is not in allowed domain.
+            [   'email' => 'fromuser@moodle.com',
+                'config' => 'example.com test.com',
+                'result' => get_string('emailonlyallowed', '', 'example.com test.com')
+            ],
+            // Test from email is not in allowed subdomain.
+            [   'email' => 'fromuser@something.example.com',
+                'config' => 'example.com test.com',
+                'result' => get_string('emailonlyallowed', '', 'example.com test.com')
+            ],
+        ];
+    }
+
+    /**
+     * Test denyemailaddresses setting.
+     *
+     * @param string $email Email address for the from user.
+     * @param string $config The CFG->denyemailaddresses config values
+     * @param false/string $result The expected result.
+     *
+     * @dataProvider data_email_is_not_allowed_for_denyemailaddresses
+     */
+    public function test_email_is_not_allowed_for_denyemailaddresses($email, $config, $result) {
+        $this->resetAfterTest();
+
+        set_config('denyemailaddresses', $config);
+        $this->assertEquals($result, email_is_not_allowed($email));
+    }
+
+
+    /**
+     * Data provider for test_email_is_not_allowed_for_denyemailaddresses.
+     *
+     * @return array Returns an array of test data for the above function.
+     */
+    public function data_email_is_not_allowed_for_denyemailaddresses() {
+        return [
+            // Test denied domain empty list.
+            [
+                'email' => 'fromuser@example.com',
+                'config' => '',
+                'result' => false
+            ],
+            // Test from email is in denied domain.
+            [
+                'email' => 'fromuser@example.com',
+                'config' => 'example.com test.com',
+                'result' => get_string('emailnotallowed', '', 'example.com test.com')
+            ],
+            // Test from email is in denied domain but uppercase config.
+            [
+                'email' => 'fromuser@example.com',
+                'config' => 'EXAMPLE.com test.com',
+                'result' => get_string('emailnotallowed', '', 'EXAMPLE.com test.com')
+            ],
+            // Test from email is in denied domain but uppercase email.
+            [
+                'email' => 'fromuser@EXAMPLE.com',
+                'config' => 'example.com test.com',
+                'result' => get_string('emailnotallowed', '', 'example.com test.com')
+            ],
+            // Test from email is in denied subdomain.
+            [
+                'email' => 'fromuser@something.example.com',
+                'config' => '.example.com test.com',
+                'result' => get_string('emailnotallowed', '', '.example.com test.com')
+            ],
+            // Test from email is in denied subdomain but uppercase config.
+            [
+                'email' => 'fromuser@something.example.com',
+                'config' => '.EXAMPLE.com test.com',
+                'result' => get_string('emailnotallowed', '', '.EXAMPLE.com test.com')
+            ],
+            // Test from email is in denied subdomain but uppercase email.
+            [
+                'email' => 'fromuser@something.EXAMPLE.com',
+                'config' => '.example.com test.com',
+                'result' => get_string('emailnotallowed', '', '.example.com test.com')
+            ],
+            // Test from email is not in denied domain.
+            [   'email' => 'fromuser@moodle.com',
+                'config' => 'example.com test.com',
+                'result' => false
+            ],
+            // Test from email is not in denied subdomain.
+            [   'email' => 'fromuser@something.example.com',
+                'config' => 'example.com test.com',
+                'result' => false
+            ],
+        ];
+    }
+
     /**
      * Test safe method unserialize_array().
      */