Some of the emails sent loose styling

[santibm]

I'm testing the theme and I can see some of the mails are loosing style and translations, debugging with mailhog, I can see this error:
CSS inlining error: Compilation from source: LESS file is empty: frontend/MageOS/m137-admin-theme/es_ES/css/email-inline.less

The logs are a bit more specific, even if this log talks about an Rma module email, is also happening with a Rewards points module, I can think that this can be affection third party vendors:

Stack trace:
#0 /var/www/html/vendor/magento/framework/View/Asset/PreProcessor/AlternativeSource.php(154): Magento\Framework\Css\PreProcessor\Adapter\Less\Processor->processContent()
#1 /var/www/html/vendor/magento/framework/View/Asset/PreProcessor/AlternativeSource.php(112): Magento\Framework\View\Asset\PreProcessor\AlternativeSource->processContent()
#2 /var/www/html/vendor/magento/module-developer/Model/View/Asset/PreProcessor/PreprocessorStrategy.php(78): Magento\Framework\View\Asset\PreProcessor\AlternativeSource->process()
#3 /var/www/html/vendor/magento/framework/View/Asset/PreProcessor/Pool.php(77): Magento\Developer\Model\View\Asset\PreProcessor\PreprocessorStrategy->process()
#4 /var/www/html/vendor/magento/framework/View/Asset/Source.php(152): Magento\Framework\View\Asset\PreProcessor\Pool->process()
#5 /var/www/html/vendor/magento/framework/View/Asset/Source.php(121): Magento\Framework\View\Asset\Source->preProcess()
#6 /var/www/html/vendor/magento/framework/View/Asset/File.php(186): Magento\Framework\View\Asset\Source->getContent()
#7 /var/www/html/vendor/magento/module-email/Model/Template/Filter.php(1041): Magento\Framework\View\Asset\File->getContent()
#8 /var/www/html/vendor/magento/module-email/Model/Template/Filter.php(1065): Magento\Email\Model\Template\Filter->getCssFilesContent()
#9 [internal function]: Magento\Email\Model\Template\Filter->applyInlineCss()
#10 /var/www/html/vendor/magento/framework/Filter/Template.php(328): call_user_func()
#11 /var/www/html/vendor/magento/framework/Filter/Template.php(237): Magento\Framework\Filter\Template->afterFilter()
#12 /var/www/html/vendor/magento/module-email/Model/Template/Filter.php(1122): Magento\Framework\Filter\Template->filter()
#13 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Email\Model\Template\Filter->filter()
#14 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Email\Model\Template\Filter\Interceptor->___callParent()
#15 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Email\Model\Template\Filter\Interceptor->Magento\Framework\Interception\{closure}()
#16 /var/www/html/generated/code/Magento/Email/Model/Template/Filter/Interceptor.php(32): Magento\Email\Model\Template\Filter\Interceptor->___callPlugins()
#17 /var/www/html/vendor/magento/module-email/Model/AbstractTemplate.php(363): Magento\Email\Model\Template\Filter\Interceptor->filter()
#18 /var/www/html/vendor/magento/module-email/Model/Template.php(380): Magento\Email\Model\AbstractTemplate->getProcessedTemplate()
#19 /var/www/html/vendor/magento/framework/Mail/Template/TransportBuilder.php(380): Magento\Email\Model\Template->processTemplate()
#20 /var/www/html/vendor/magento/framework/Mail/Template/TransportBuilder.php(336): Magento\Framework\Mail\Template\TransportBuilder->prepareMessage()
#21 /var/www/html/vendor/hiberus/smtp-mail/Model/TransportBuilder.php(53): Magento\Framework\Mail\Template\TransportBuilder->getTransport()
#22 /var/www/html/generated/code/Hiberus/SmtpMail/Model/TransportBuilder/Interceptor.php(23): Hiberus\SmtpMail\Model\TransportBuilder->getTransport()
#23 /var/www/html/vendor/amasty/rma/Utils/Email.php(88): Hiberus\SmtpMail\Model\TransportBuilder\Interceptor->getTransport()
#24 /var/www/html/vendor/amasty/rma/Observer/Rma/StatusChanged.php(110): Amasty\Rma\Utils\Email->sendEmail()
#25 /var/www/html/vendor/magento/framework/Event/Invoker/InvokerDefault.php(88): Amasty\Rma\Observer\Rma\StatusChanged->execute()
#26 /var/www/html/vendor/magento/framework/Event/Invoker/InvokerDefault.php(74): Magento\Framework\Event\Invoker\InvokerDefault->_callObserverMethod()
#27 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Framework\Event\Invoker\InvokerDefault->dispatch()
#28 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Framework\Event\Invoker\InvokerDefault\Interceptor->___callParent()
#29 /var/www/html/vendor/smile/module-debug-toolbar/Plugin/Event/InvokerPlugin.php(45): Magento\Framework\Event\Invoker\InvokerDefault\Interceptor->Magento\Framework\Interception\{closure}()
#30 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(135): Smile\DebugToolbar\Plugin\Event\InvokerPlugin->aroundDispatch()
#31 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Framework\Event\Invoker\InvokerDefault\Interceptor->Magento\Framework\Interception\{closure}()
#32 /var/www/html/generated/code/Magento/Framework/Event/Invoker/InvokerDefault/Interceptor.php(23): Magento\Framework\Event\Invoker\InvokerDefault\Interceptor->___callPlugins()
#33 /var/www/html/vendor/magento/framework/Event/Manager.php(65): Magento\Framework\Event\Invoker\InvokerDefault\Interceptor->dispatch()
#34 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Framework\Event\Manager->dispatch()
#35 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Framework\Event\Manager\Interceptor->___callParent()
#36 /var/www/html/vendor/smile/module-debug-toolbar/Plugin/Event/ManagerPlugin.php(35): Magento\Framework\Event\Manager\Interceptor->Magento\Framework\Interception\{closure}()
#37 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(135): Smile\DebugToolbar\Plugin\Event\ManagerPlugin->aroundDispatch()
#38 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Framework\Event\Manager\Interceptor->Magento\Framework\Interception\{closure}()
#39 /var/www/html/generated/code/Magento/Framework/Event/Manager/Interceptor.php(23): Magento\Framework\Event\Manager\Interceptor->___callPlugins()
#40 /var/www/html/generated/code/Magento/Framework/Event/Manager/Proxy.php(95): Magento\Framework\Event\Manager\Interceptor->dispatch()
#41 /var/www/html/vendor/amasty/rma/Model/Request/Repository.php(201): Magento\Framework\Event\Manager\Proxy->dispatch()
#42 /var/www/html/vendor/amasty/rma/Controller/Adminhtml/Request/Save.php(147): Amasty\Rma\Model\Request\Repository->save()
#43 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(58): Amasty\Rma\Controller\Adminhtml\Request\Save->execute()
#44 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(138): Amasty\Rma\Controller\Adminhtml\Request\Save\Interceptor->___callParent()
#45 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Amasty\Rma\Controller\Adminhtml\Request\Save\Interceptor->Magento\Framework\Interception\{closure}()
#46 /var/www/html/generated/code/Amasty/Rma/Controller/Adminhtml/Request/Save/Interceptor.php(23): Amasty\Rma\Controller\Adminhtml\Request\Save\Interceptor->___callPlugins()
#47 /var/www/html/vendor/magento/framework/App/Action/Action.php(111): Amasty\Rma\Controller\Adminhtml\Request\Save\Interceptor->execute()
#48 /var/www/html/vendor/magento/module-backend/App/AbstractAction.php(151): Magento\Framework\App\Action\Action->dispatch()
#49 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Backend\App\AbstractAction->dispatch()
#50 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(138): Amasty\Rma\Controller\Adminhtml\Request\Save\Interceptor->___callParent()
#51 /var/www/html/vendor/magento/module-backend/App/Action/Plugin/Authentication.php(145): Amasty\Rma\Controller\Adminhtml\Request\Save\Interceptor->Magento\Framework\Interception\{closure}()
#52 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(135): Magento\Backend\App\Action\Plugin\Authentication->aroundDispatch()
#53 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Amasty\Rma\Controller\Adminhtml\Request\Save\Interceptor->Magento\Framework\Interception\{closure}()
#54 /var/www/html/generated/code/Amasty/Rma/Controller/Adminhtml/Request/Save/Interceptor.php(32): Amasty\Rma\Controller\Adminhtml\Request\Save\Interceptor->___callPlugins()
#55 /var/www/html/vendor/magento/framework/App/FrontController.php(245): Amasty\Rma\Controller\Adminhtml\Request\Save\Interceptor->dispatch()
#56 /var/www/html/vendor/magento/framework/App/FrontController.php(212): Magento\Framework\App\FrontController->getActionResponse()
#57 /var/www/html/vendor/magento/framework/App/FrontController.php(147): Magento\Framework\App\FrontController->processRequest()
#58 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Framework\App\FrontController->dispatch()
#59 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Framework\App\FrontController\Interceptor->___callParent()
#60 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Framework\App\FrontController\Interceptor->Magento\Framework\Interception\{closure}()
#61 /var/www/html/generated/code/Magento/Framework/App/FrontController/Interceptor.php(23): Magento\Framework\App\FrontController\Interceptor->___callPlugins()
#62 /var/www/html/vendor/magento/framework/App/Http.php(116): Magento\Framework\App\FrontController\Interceptor->dispatch()
#63 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Framework\App\Http->launch()
#64 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Framework\App\Http\Interceptor->___callParent()
#65 /var/www/html/vendor/yireo/magento2-whoops/Plugin/HttpApp.php(102): Magento\Framework\App\Http\Interceptor->Magento\Framework\Interception\{closure}()
#66 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(135): Yireo\Whoops\Plugin\HttpApp->aroundLaunch()
#67 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Framework\App\Http\Interceptor->Magento\Framework\Interception\{closure}()
#68 /var/www/html/generated/code/Magento/Framework/App/Http/Interceptor.php(23): Magento\Framework\App\Http\Interceptor->___callPlugins()
#69 /var/www/html/vendor/magento/framework/App/Bootstrap.php(264): Magento\Framework\App\Http\Interceptor->launch()
#70 /var/www/html/pub/index.php(40): Magento\Framework\App\Bootstrap->run()
#71 {main} [] []

[rhoerr]

Do you know if these emails are aimed at customers or administrators? I would expect any customer-facing emails, if not all emails across the board, to use the frontend theme and scope, in which case the admin theme shouldn't enter into it. There are some admin emails for password resets, 2FA, security alerts, but if these are customer facing, it seems like possibly an issue on the extension's side (Amasty in this case).

[davidtabat]

@santibm I managed to replicate this issue on my project, it was related to switcher module not theme module itself.
Fix is available in latest release of the switcher module (1.1.1)
mage-os-lab/module-theme-adminhtml-switcher#6

Let me know if it solves the issue for you.

[santibm]

Sorry for the delay, just updated the theme and switcher and those emails are now perfectly translated! Thanks a lot!!