askvortsov don't judge idk if this is what you want, but I accessed the latest log and this error msg is all over the file:
[2020-08-06 19:11:39] production.ERROR: Swift_TransportException: Expected response code 220 but got an empty response in /var/www/html/tretoko.com/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php:445
Stack trace:
#0 /var/www/html/tretoko.com/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php(358): Swift_Transport_AbstractSmtpTransport->assertResponseCode()
#1 /var/www/html/tretoko.com/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php(147): Swift_Transport_AbstractSmtpTransport->readGreeting()
#2 /var/www/html/tretoko.com/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/SendmailTransport.php(50): Swift_Transport_AbstractSmtpTransport->start()
#3 /var/www/html/tretoko.com/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mailer.php(65): Swift_Transport_SendmailTransport->start()
#4 /var/www/html/tretoko.com/vendor/illuminate/mail/Mailer.php(483): Swift_Mailer->send()
#5 /var/www/html/tretoko.com/vendor/illuminate/mail/Mailer.php(259): Illuminate\Mail\Mailer->sendSwiftMessage()
#6 /var/www/html/tretoko.com/vendor/flarum/core/src/Notification/NotificationMailer.php(43): Illuminate\Mail\Mailer->send()
#7 /var/www/html/tretoko.com/vendor/flarum/core/src/Notification/Job/SendEmailNotificationJob.php(37): Flarum\Notification\NotificationMailer->send()
#8 [internal function]: Flarum\Notification\Job\SendEmailNotificationJob->handle()
#9 /var/www/html/tretoko.com/vendor/illuminate/container/BoundMethod.php(29): call_user_func_array()
#10 /var/www/html/tretoko.com/vendor/illuminate/container/BoundMethod.php(87): Illuminate\Container\BoundMethod::Illuminate\Container{closure}()
#11 /var/www/html/tretoko.com/vendor/illuminate/container/BoundMethod.php(31): Illuminate\Container\BoundMethod::callBoundMethod()
#12 /var/www/html/tretoko.com/vendor/illuminate/container/Container.php(572): Illuminate\Container\BoundMethod::call()
#13 /var/www/html/tretoko.com/vendor/illuminate/bus/Dispatcher.php(94): Illuminate\Container\Container->call()
#14 /var/www/html/tretoko.com/vendor/illuminate/pipeline/Pipeline.php(128): Illuminate\Bus\Dispatcher->Illuminate\Bus{closure}()
#15 /var/www/html/tretoko.com/vendor/illuminate/pipeline/Pipeline.php(104): Illuminate\Pipeline\Pipeline->Illuminate\Pipeline{closure}()
#16 /var/www/html/tretoko.com/vendor/illuminate/bus/Dispatcher.php(98): Illuminate\Pipeline\Pipeline->then()
#17 /var/www/html/tretoko.com/vendor/illuminate/queue/CallQueuedHandler.php(49): Illuminate\Bus\Dispatcher->dispatchNow()
#18 /var/www/html/tretoko.com/vendor/illuminate/queue/Jobs/Job.php(83): Illuminate\Queue\CallQueuedHandler->call()
#19 /var/www/html/tretoko.com/vendor/illuminate/queue/SyncQueue.php(42): Illuminate\Queue\Jobs\Job->fire()
#20 /var/www/html/tretoko.com/vendor/flarum/core/src/Notification/NotificationSyncer.php(163): Illuminate\Queue\SyncQueue->push()
#21 /var/www/html/tretoko.com/vendor/flarum/core/src/Notification/NotificationSyncer.php(110): Flarum\Notification\NotificationSyncer->mailNotifications()
#22 /var/www/html/tretoko.com/vendor/flarum/subscriptions/src/Job/SendReplyNotification.php(57): Flarum\Notification\NotificationSyncer->sync()
#23 [internal function]: Flarum\Subscriptions\Job\SendReplyNotification->handle()
#24 /var/www/html/tretoko.com/vendor/illuminate/container/BoundMethod.php(29): call_user_func_array()
#25 /var/www/html/tretoko.com/vendor/illuminate/container/BoundMethod.php(87): Illuminate\Container\BoundMethod::Illuminate\Container{closure}()
#26 /var/www/html/tretoko.com/vendor/illuminate/container/BoundMethod.php(31): Illuminate\Container\BoundMethod::callBoundMethod()
#27 /var/www/html/tretoko.com/vendor/illuminate/container/Container.php(572): Illuminate\Container\BoundMethod::call()
#28 /var/www/html/tretoko.com/vendor/illuminate/bus/Dispatcher.php(94): Illuminate\Container\Container->call()
#29 /var/www/html/tretoko.com/vendor/illuminate/pipeline/Pipeline.php(128): Illuminate\Bus\Dispatcher->Illuminate\Bus{closure}()
#30 /var/www/html/tretoko.com/vendor/illuminate/pipeline/Pipeline.php(104): Illuminate\Pipeline\Pipeline->Illuminate\Pipeline{closure}()
#31 /var/www/html/tretoko.com/vendor/illuminate/bus/Dispatcher.php(98): Illuminate\Pipeline\Pipeline->then()
#32 /var/www/html/tretoko.com/vendor/illuminate/queue/CallQueuedHandler.php(49): Illuminate\Bus\Dispatcher->dispatchNow()
#33 /var/www/html/tretoko.com/vendor/illuminate/queue/Jobs/Job.php(83): Illuminate\Queue\CallQueuedHandler->call()
#34 /var/www/html/tretoko.com/vendor/illuminate/queue/SyncQueue.php(42): Illuminate\Queue\Jobs\Job->fire()
#35 /var/www/html/tretoko.com/vendor/flarum/subscriptions/src/Listener/SendNotificationWhenReplyIsPosted.php(31): Illuminate\Queue\SyncQueue->push()
#36 [internal function]: Flarum\Subscriptions\Listener\SendNotificationWhenReplyIsPosted->handle()
#37 /var/www/html/tretoko.com/vendor/illuminate/events/Dispatcher.php(379): call_user_func_array()
#38 /var/www/html/tretoko.com/vendor/illuminate/events/Dispatcher.php(209): Illuminate\Events\Dispatcher->Illuminate\Events{closure}()
#39 /var/www/html/tretoko.com/vendor/flarum/core/src/Foundation/DispatchEventsTrait.php(33): Illuminate\Events\Dispatcher->dispatch()
#40 /var/www/html/tretoko.com/vendor/flarum/core/src/Post/Command/PostReplyHandler.php(106): Flarum\Post\Command\PostReplyHandler->dispatchEventsFor()
#41 /var/www/html/tretoko.com/vendor/flarum/core/src/Notification/NotificationSyncer.php(148): Flarum\Post\Command\PostReplyHandler->Flarum\Post\Command{closure}()
#42 /var/www/html/tretoko.com/vendor/flarum/core/src/Post/Command/PostReplyHandler.php(107): Flarum\Notification\NotificationSyncer->onePerUser()
#43 /var/www/html/tretoko.com/vendor/illuminate/bus/Dispatcher.php(90): Flarum\Post\Command\PostReplyHandler->handle()
#44 /var/www/html/tretoko.com/vendor/illuminate/pipeline/Pipeline.php(128): Illuminate\Bus\Dispatcher->Illuminate\Bus{closure}()
#45 /var/www/html/tretoko.com/vendor/illuminate/pipeline/Pipeline.php(104): Illuminate\Pipeline\Pipeline->Illuminate\Pipeline{closure}()
#46 /var/www/html/tretoko.com/vendor/illuminate/bus/Dispatcher.php(98): Illuminate\Pipeline\Pipeline->then()
#47 /var/www/html/tretoko.com/vendor/illuminate/bus/Dispatcher.php(76): Illuminate\Bus\Dispatcher->dispatchNow()
#48 /var/www/html/tretoko.com/vendor/flarum/core/src/Api/Controller/CreatePostController.php(73): Illuminate\Bus\Dispatcher->dispatch()
#49 /var/www/html/tretoko.com/vendor/flarum/core/src/Api/Controller/AbstractSerializeController.php(96): Flarum\Api\Controller\CreatePostController->data()
#50 /var/www/html/tretoko.com/vendor/flarum/core/src/Api/Controller/AbstractCreateController.php(22): Flarum\Api\Controller\AbstractSerializeController->handle()
#51 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/RouteHandlerFactory.php(38): Flarum\Api\Controller\AbstractCreateController->handle()
#52 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/Middleware/DispatchRoute.php(65): Flarum\Http\RouteHandlerFactory->Flarum\Http{closure}()
#53 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Flarum\Http\Middleware\DispatchRoute->process()
#54 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/Middleware/SetLocale.php(50): Laminas\Stratigility\Next->handle()
#55 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Flarum\Http\Middleware\SetLocale->process()
#56 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/Middleware/CheckCsrfToken.php(45): Laminas\Stratigility\Next->handle()
#57 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Flarum\Http\Middleware\CheckCsrfToken->process()
#58 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/Middleware/AuthenticateWithHeader.php(55): Laminas\Stratigility\Next->handle()
#59 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Flarum\Http\Middleware\AuthenticateWithHeader->process()
#60 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/Middleware/AuthenticateWithSession.php(32): Laminas\Stratigility\Next->handle()
#61 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Flarum\Http\Middleware\AuthenticateWithSession->process()
#62 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/Middleware/RememberFromCookie.php(51): Laminas\Stratigility\Next->handle()
#63 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Flarum\Http\Middleware\RememberFromCookie->process()
#64 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/Middleware/StartSession.php(61): Laminas\Stratigility\Next->handle()
#65 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Flarum\Http\Middleware\StartSession->process()
#66 /var/www/html/tretoko.com/vendor/flarum/core/src/Api/Middleware/FakeHttpMethods.php(29): Laminas\Stratigility\Next->handle()
#67 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Flarum\Api\Middleware\FakeHttpMethods->process()
#68 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/Middleware/ParseJsonBody.php(28): Laminas\Stratigility\Next->handle()
#69 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Flarum\Http\Middleware\ParseJsonBody->process()
#70 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/Middleware/HandleErrors.php(57): Laminas\Stratigility\Next->handle()
#71 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Flarum\Http\Middleware\HandleErrors->process()
#72 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(84): Laminas\Stratigility\Next->handle()
#73 /var/www/html/tretoko.com/vendor/middlewares/request-handler/src/RequestHandler.php(84): Laminas\Stratigility\MiddlewarePipe->process()
#74 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Middlewares\RequestHandler->process()
#75 /var/www/html/tretoko.com/vendor/middlewares/base-path-router/src/BasePathRouter.php(97): Laminas\Stratigility\Next->handle()
#76 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Middlewares\BasePathRouter->process()
#77 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Middleware/OriginalMessages.php(42): Laminas\Stratigility\Next->handle()
#78 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Laminas\Stratigility\Middleware\OriginalMessages->process()
#79 /var/www/html/tretoko.com/vendor/middlewares/base-path/src/BasePath.php(53): Laminas\Stratigility\Next->handle()
#80 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/Next.php(61): Middlewares\BasePath->process()
#81 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(84): Laminas\Stratigility\Next->handle()
#82 /var/www/html/tretoko.com/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(73): Laminas\Stratigility\MiddlewarePipe->process()
#83 /var/www/html/tretoko.com/vendor/laminas/laminas-httphandlerrunner/src/RequestHandlerRunner.php(96): Laminas\Stratigility\MiddlewarePipe->handle()
#84 /var/www/html/tretoko.com/vendor/flarum/core/src/Http/Server.php(42): Laminas\HttpHandlerRunner\RequestHandlerRunner->run()
#85 /var/www/html/tretoko.com/index.php(26): Flarum\Http\Server->listen()