diff --git a/typo3/sysext/core/Configuration/DefaultConfiguration.php b/typo3/sysext/core/Configuration/DefaultConfiguration.php
index bd5bf51027a39a17d18e03370f7170493f45401f..d4ba12d8afd7c18b52960e48c5f33ecede2ce8e9 100644
--- a/typo3/sysext/core/Configuration/DefaultConfiguration.php
+++ b/typo3/sysext/core/Configuration/DefaultConfiguration.php
@@ -1361,7 +1361,7 @@ return [
     'MAIL' => [ // Mail configurations to tune how \TYPO3\CMS\Core\Mail\ classes will send their mails.
         'transport' => 'sendmail',
         'transport_smtp_server' => 'localhost:25',
-        'transport_smtp_encrypt' => '',
+        'transport_smtp_encrypt' => false,
         'transport_smtp_username' => '',
         'transport_smtp_password' => '',
         'transport_sendmail_command' => '',
diff --git a/typo3/sysext/install/Classes/Service/SilentConfigurationUpgradeService.php b/typo3/sysext/install/Classes/Service/SilentConfigurationUpgradeService.php
index 5f076055f15855c0ec63f776c10a973bc1f8e981..d16b622ee9ccd2651c60f3595a8ed6a3aae695ce 100644
--- a/typo3/sysext/install/Classes/Service/SilentConfigurationUpgradeService.php
+++ b/typo3/sysext/install/Classes/Service/SilentConfigurationUpgradeService.php
@@ -1130,6 +1130,8 @@ class SilentConfigurationUpgradeService
                         // Due to the misleading name (transport_smtp_encrypt) we avoid to set the option to false, but rather remove it.
                         // Note: symfony/mailer provides no way to enforce STARTTLS usage, see https://github.com/symfony/symfony/commit/5b8c4676d059
                         $confManager->removeLocalConfigurationKeysByPath(['MAIL/transport_smtp_encrypt']);
+                    } elseif ($encrypt === '') {
+                        $confManager->setLocalConfigurationValueByPath('MAIL/transport_smtp_encrypt', false);
                     } else {
                         $confManager->setLocalConfigurationValueByPath('MAIL/transport_smtp_encrypt', true);
                     }