diff --git a/lib/phpunit/bootstrap.php b/lib/phpunit/bootstrap.php
index 4d573df0b00..add63122157 100644
--- a/lib/phpunit/bootstrap.php
+++ b/lib/phpunit/bootstrap.php
@@ -209,8 +209,6 @@ error_reporting($CFG->debug);
 ini_set('display_errors', '1');
 ini_set('log_errors', '1');
 
-$CFG->noemailever = true; // better not mail anybody from tests, override temporarily if necessary
-
 // some ugly hacks
 $CFG->themerev = 1;
 $CFG->jsrev = 1;
diff --git a/lib/phpunit/classes/util.php b/lib/phpunit/classes/util.php
index c5e408b3ae7..1c1928e0ff7 100644
--- a/lib/phpunit/classes/util.php
+++ b/lib/phpunit/classes/util.php
@@ -106,12 +106,15 @@ class phpunit_util extends testing_util {
         // Stop any message redirection.
         phpunit_util::stop_message_redirection();
 
-        // Stop any message redirection.
-        phpunit_util::stop_phpmailer_redirection();
-
         // Stop any message redirection.
         phpunit_util::stop_event_redirection();
 
+        // Start a new email redirection.
+        // This will clear any existing phpmailer redirection.
+        // We redirect all phpmailer output to this message sink which is
+        // called instead of phpmailer actually sending the message.
+        phpunit_util::start_phpmailer_redirection();
+
         // We used to call gc_collect_cycles here to ensure desctructors were called between tests.
         // This accounted for 25% of the total time running phpunit - so we removed it.
 
@@ -678,9 +681,11 @@ class phpunit_util extends testing_util {
      */
     public static function start_phpmailer_redirection() {
         if (self::$phpmailersink) {
-            self::stop_phpmailer_redirection();
+            // If an existing mailer sink is active, just clear it.
+            self::$phpmailersink->clear();
+        } else {
+            self::$phpmailersink = new phpunit_phpmailer_sink();
         }
-        self::$phpmailersink = new phpunit_phpmailer_sink();
         return self::$phpmailersink;
     }
 
diff --git a/lib/upgrade.txt b/lib/upgrade.txt
index 79e608d706b..7ea8021503a 100644
--- a/lib/upgrade.txt
+++ b/lib/upgrade.txt
@@ -4,6 +4,9 @@ information provided here is intended especially for developers.
 === 2.9 ===
 
 * \core\event\course_viewed 'other' argument renamed from coursesectionid to coursesectionnumber as it contains the section number.
+* PHPUnit: PHPMailer Sink is now started for all tests and is setup within the phpunit wrapper for advanced tests.
+  Catching debugging messages when sending mail will no longer work. Use $sink = $this->redirectEmails(); and then check
+  the message in the sink instead.
 
 === 2.8 ===