"Error sending email: An email must have a "To", "Cc", or "Bcc" header."

This module doesn't have a cron function, so I guess your email is likely being generated by another module, and that is where the bug is.

Thanks, is there any way to enabel stack trace?

The error is generated by symfony but no stacktrace is being shown to allow tracking of error.

We have the same issue. Normally there's no stacktrace provided, but when enabling Reroute Email the stack is printed (with the same problem).

#0 /var/www/html/modules/contrib/reroute_email/src/RerouteEmailHandlerPluginBase.php(43): Drupal\reroute_email\Plugin\RerouteEmailHandler\HookMailAlter->setHeader('X-Rerouted-Orig...', NULL)
#1 /var/www/html/modules/contrib/reroute_email/src/RerouteEmailHandlerPluginManager.php(77): Drupal\reroute_email\RerouteEmailHandlerPluginBase->process()
#2 /var/www/html/modules/contrib/reroute_email/reroute_email.module(47): Drupal\reroute_email\RerouteEmailHandlerPluginManager->processAllByType('hook_mail_alter', Array)
#3 /var/www/html/core/lib/Drupal/Core/Extension/ModuleHandler.php(552): reroute_email_mail_alter(Array, NULL, NULL)
#4 /var/www/html/modules/contrib/symfony_mailer/src/Plugin/EmailBuilder/LegacyEmailBuilder.php(128): Drupal\Core\Extension\ModuleHandler->alter('mail', Array)
#5 [internal function]: Drupal\symfony_mailer\Plugin\EmailBuilder\LegacyEmailBuilder->build(Object(Drupal\symfony_mailer\Email))
#6 /var/www/html/modules/contrib/symfony_mailer/src/Email.php(490): call_user_func(Array, Object(Drupal\symfony_mailer\Email))
#7 /var/www/html/modules/contrib/symfony_mailer/src/Mailer.php(179): Drupal\symfony_mailer\Email->process()
#8 /var/www/html/modules/contrib/symfony_mailer/src/Mailer.php(149): Drupal\symfony_mailer\Mailer->doSend(Object(Drupal\symfony_mailer\Email))
#9 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(638): Drupal\symfony_mailer\Mailer->Drupal\symfony_mailer\{closure}()
#10 /var/www/html/modules/contrib/symfony_mailer/src/Mailer.php(147): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure))
#11 /var/www/html/modules/contrib/symfony_mailer/src/Email.php(292): Drupal\symfony_mailer\Mailer->send(Object(Drupal\symfony_mailer\Email))
#12 /var/www/html/modules/contrib/symfony_mailer/src/MailManagerReplacement.php(92): Drupal\symfony_mailer\Email->send()
#13 /var/www/html/core/modules/update/update.fetch.inc(44): Drupal\symfony_mailer\MailManagerReplacement->mail('update', 'status_notify', '', 'de', Array)
#14 /var/www/html/core/modules/update/update.module(188): _update_cron_notify()
#15 /var/www/html/core/lib/Drupal/Core/Cron.php(337): update_cron()
#16 /var/www/html/core/lib/Drupal/Core/Extension/ModuleHandler.php(395): Drupal\Core\Cron->Drupal\Core\{closure}(Object(Closure), 'update')
#17 /var/www/html/core/lib/Drupal/Core/Cron.php(320): Drupal\Core\Extension\ModuleHandler->invokeAllWith('cron', Object(Closure))
#18 /var/www/html/core/lib/Drupal/Core/Cron.php(159): Drupal\Core\Cron->invokeCronHandlers()
#19 /var/www/html/core/lib/Drupal/Core/ProxyClass/Cron.php(75): Drupal\Core\Cron->run()
#20 /var/www/html/core/modules/system/src/CronController.php(38): Drupal\Core\ProxyClass\Cron->run()
#21 [internal function]: Drupal\system\CronController->run()
#22 /var/www/html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array)
#23 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(638): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#24 /var/www/html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(121): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure))
#25 /var/www/html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array)
#26 /var/www/vendor/symfony/http-kernel/HttpKernel.php(181): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#27 /var/www/vendor/symfony/http-kernel/HttpKernel.php(76): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#28 /var/www/html/core/lib/Drupal/Core/StackMiddleware/Session.php(53): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#29 /var/www/html/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#30 /var/www/html/core/lib/Drupal/Core/StackMiddleware/ContentLength.php(28): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#31 /var/www/html/core/modules/page_cache/src/StackMiddleware/PageCache.php(201): Drupal\Core\StackMiddleware\ContentLength->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#32 /var/www/html/core/modules/page_cache/src/StackMiddleware/PageCache.php(138): Drupal\page_cache\StackMiddleware\PageCache->fetch(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#33 /var/www/html/core/modules/page_cache/src/StackMiddleware/PageCache.php(87): Drupal\page_cache\StackMiddleware\PageCache->lookup(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#34 /var/www/html/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#35 /var/www/html/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#36 /var/www/html/core/lib/Drupal/Core/StackMiddleware/AjaxPageState.php(36): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#37 /var/www/html/core/lib/Drupal/Core/StackMiddleware/StackedHttpKernel.php(51): Drupal\Core\StackMiddleware\AjaxPageState->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#38 /var/www/html/core/lib/Drupal/Core/DrupalKernel.php(741): Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#39 /var/www/html/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#40 {main}

It seems to be an issue with the update manager when no email addresses are set. Then the _update_cron_notify function in the module sends emails without a recipient.

→

@daniel.pernold

Thanks, confirmed and resolved by adding email address.