So i've set up my mailserver and everything is now up and running, i've checked also the functionality by mailing a mail to myself via googlemail and it worked, and yet i get stil those lenghty errors via debug info.
`POST https://mydomain.eu/social/public/api/mail/test
Swift_TransportException: Expected response code 250 but got code "221", with message "221 2.7.0 Error: I can break rules, too. Goodbye.
" in /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php:459
Stack trace:
#0 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php(344): Swift_Transport_AbstractSmtpTransport->assertResponseCode('221 2.7.0 Error...', Array)
#1 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php(366): Swift_Transport_AbstractSmtpTransport->executeCommand('HELO mydomain.e...', Array)
#2 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php(148): Swift_Transport_AbstractSmtpTransport->doHeloCommand()
#3 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/SendmailTransport.php(50): Swift_Transport_AbstractSmtpTransport->start()
#4 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mailer.php(65): Swift_Transport_SendmailTransport->start()
#5 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/illuminate/mail/Mailer.php(521): Swift_Mailer->send(Object(Swift_Message), Array)
#6 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/illuminate/mail/Mailer.php(288): Illuminate\Mail\Mailer->sendSwiftMessage(Object(Swift_Message))
#7 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/illuminate/mail/Mailer.php(212): Illuminate\Mail\Mailer->send(NULL, Array, Object(Closure))
#8 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Api/Controller/SendTestMailController.php(40): Illuminate\Mail\Mailer->raw('Hey ungarich!\n\n...', Object(Closure))
#9 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/RouteHandlerFactory.php(41): Flarum\Api\Controller\SendTestMailController->handle(Object(Laminas\Diactoros\ServerRequest))
#10 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/ExecuteRoute.php(27): Flarum\Http\RouteHandlerFactory->Flarum\Http{closure}(Object(Laminas\Diactoros\ServerRequest), Array)
#11 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\ExecuteRoute->process(Object(Laminas\Diactoros\ServerRequest), Object(Closure))
#12 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/clarkwinkelmann/flarum-ext-readonly-profile/src/AbstractMiddleware.php(22): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#13 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): ClarkWinkelmann\ReadonlyProfile\AbstractMiddleware->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#14 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Api/Middleware/ThrottleApi.php(33): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#15 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Api\Middleware\ThrottleApi->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#16 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/CheckCsrfToken.php(44): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#17 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\CheckCsrfToken->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#18 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/ResolveRoute.php(69): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#19 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\ResolveRoute->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#20 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/SetLocale.php(51): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#21 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\SetLocale->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#22 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/AuthenticateWithHeader.php(58): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#23 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\AuthenticateWithHeader->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#24 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/AuthenticateWithSession.php(31): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#25 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\AuthenticateWithSession->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#26 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/RememberFromCookie.php(52): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#27 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\RememberFromCookie->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#28 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/StartSession.php(61): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#29 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\StartSession->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#30 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Api/Middleware/FakeHttpMethods.php(29): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#31 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Api\Middleware\FakeHttpMethods->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#32 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/ParseJsonBody.php(28): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#33 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\ParseJsonBody->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#34 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/HandleErrors.php(57): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#35 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\HandleErrors->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#36 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/InjectActorReference.php(25): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#37 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\InjectActorReference->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#38 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(77): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#39 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/middlewares/request-handler/src/RequestHandler.php(84): Laminas\Stratigility\MiddlewarePipe->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#40 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Middlewares\RequestHandler->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#41 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/middlewares/base-path-router/src/BasePathRouter.php(99): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#42 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Middlewares\BasePathRouter->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#43 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Middleware/OriginalMessages.php(36): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#44 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Laminas\Stratigility\Middleware\OriginalMessages->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#45 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/middlewares/base-path/src/BasePath.php(73): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#46 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Middlewares\BasePath->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#47 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Middleware/ProcessIp.php(24): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#48 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/Next.php(52): Flarum\Http\Middleware\ProcessIp->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\Next))
#49 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(77): Laminas\Stratigility\Next->handle(Object(Laminas\Diactoros\ServerRequest))
#50 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(66): Laminas\Stratigility\MiddlewarePipe->process(Object(Laminas\Diactoros\ServerRequest), Object(Laminas\Stratigility\EmptyPipelineHandler))
#51 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/laminas/laminas-httphandlerrunner/src/RequestHandlerRunner.php(73): Laminas\Stratigility\MiddlewarePipe->handle(Object(Laminas\Diactoros\ServerRequest))
#52 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/vendor/flarum/core/src/Http/Server.php(45): Laminas\HttpHandlerRunner\RequestHandlerRunner->run()
#53 /var/www/vhosts/myhoster/mydomain.eu/httpdocs/social/public/index.php(26): Flarum\Http\Server->listen()
#54 {main}`
Installed vanilla (O.S.) forums too to check if there are simillar problems but everything runs fine.
I have absolutey no idea what i could try as next. :/