我的应用程序出现此错误，但我不知道如何修复它。我唯一知道的是，这是我自动发送的电子邮件的问题。我使用 Mailgun 来实现此目的，并且该应用程序位于 Laravel 上。
就是这个错误，不知道有没有同样问题的人可以帮助我。
[2022-06-25 13:52:41] production.ERROR: Expected response code "250/251/252" but got code "501", with message "501 Invalid command or cannot parse to address". {"exception":"[object] (Symfony\\Component\\Mailer\\Exception\\TransportException(code: 501): Expected response code \"250/251/252\" but got code \"501\", with message \"501 Invalid command or cannot parse to address\". at /var/www/main/vendor/symfony/mailer/Transport/Smtp/SmtpTransport.php:308)
[stacktrace]
#0 /var/www/main/vendor/symfony/mailer/Transport/Smtp/SmtpTransport.php(182): Symfony\\Component\\Mailer\\Transport\\Smtp\\SmtpTransport->assertResponseCode()
#1 /var/www/main/vendor/symfony/mailer/Transport/Smtp/SmtpTransport.php(240): Symfony\\Component\\Mailer\\Transport\\Smtp\\SmtpTransport->executeCommand()
#2 /var/www/main/vendor/symfony/mailer/Transport/Smtp/SmtpTransport.php(201): Symfony\\Component\\Mailer\\Transport\\Smtp\\SmtpTransport->doRcptToCommand()
#3 /var/www/main/vendor/symfony/mailer/Transport/AbstractTransport.php(68): Symfony\\Component\\Mailer\\Transport\\Smtp\\SmtpTransport->doSend()
#4 /var/www/main/vendor/symfony/mailer/Transport/Smtp/SmtpTransport.php(136): Symfony\\Component\\Mailer\\Transport\\AbstractTransport->send()
#5 /var/www/main/vendor/laravel/framework/src/Illuminate/Mail/Mailer.php(521): Symfony\\Component\\Mailer\\Transport\\Smtp\\SmtpTransport->send()
#6 /var/www/main/vendor/laravel/framework/src/Illuminate/Mail/Mailer.php(285): Illuminate\\Mail\\Mailer->sendSymfonyMessage()
#7 /var/www/main/vendor/laravel/framework/src/Illuminate/Mail/Mailable.php(210): Illuminate\\Mail\\Mailer->send()
#8 /var/www/main/vendor/laravel/framework/src/Illuminate/Support/Traits/Localizable.php(19): Illuminate\\Mail\\Mailable->Illuminate\\Mail\\{closure}()
#9 /var/www/main/vendor/laravel/framework/src/Illuminate/Mail/Mailable.php(211): Illuminate\\Mail\\Mailable->withLocale()
#10 /var/www/main/vendor/laravel/framework/src/Illuminate/Mail/Mailer.php(307): Illuminate\\Mail\\Mailable->send()
#11 /var/www/main/vendor/laravel/framework/src/Illuminate/Mail/Mailer.php(253): Illuminate\\Mail\\Mailer->sendMailable()
#12 /var/www/main/vendor/laravel/framework/src/Illuminate/Mail/PendingMail.php(124): Illuminate\\Mail\\Mailer->send()
#13 /var/www/main/app/Http/Controllers/MetricController.php(39): Illuminate\\Mail\\PendingMail->send()
#14 /var/www/main/vendor/laravel/framework/src/Illuminate/Routing/Controller.php(54): App\\Http\\Controllers\\MetricController->sendEmailWithCoupon()
#15 /var/www/main/vendor/laravel/framework/src/Illuminate/Routing/ControllerDispatcher.php(45): Illuminate\\Routing\\Controller->callAction()
#16 /var/www/main/vendor/laravel/framework/src/Illuminate/Routing/Route.php(261): Illuminate\\Routing\\ControllerDispatcher->dispatch()
#17 /var/www/main/vendor/laravel/framework/src/Illuminate/Routing/Route.php(204): Illuminate\\Routing\\Route->runController()
#18 /var/www/main/vendor/laravel/framework/src/Illuminate/Routing/Router.php(725): Illuminate\\Routing\\Route->run()
#19 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(141): Illuminate\\Routing\\Router->Illuminate\\Routing\\{closure}()
#20 /var/www/main/app/Http/Middleware/CorsMiddleware.php(52): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#21 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): App\\Http\\Middleware\\CorsMiddleware->handle()
#22 /var/www/main/vendor/laravel/framework/src/Illuminate/Routing/Middleware/SubstituteBindings.php(50): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#23 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Routing\\Middleware\\SubstituteBindings->handle()
#24 /var/www/main/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/VerifyCsrfToken.php(78): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#25 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Foundation\\Http\\Middleware\\VerifyCsrfToken->handle()
#26 /var/www/main/vendor/laravel/framework/src/Illuminate/View/Middleware/ShareErrorsFromSession.php(49): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#27 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\View\\Middleware\\ShareErrorsFromSession->handle()
#28 /var/www/main/vendor/laravel/framework/src/Illuminate/Session/Middleware/StartSession.php(121): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#29 /var/www/main/vendor/laravel/framework/src/Illuminate/Session/Middleware/StartSession.php(64): Illuminate\\Session\\Middleware\\StartSession->handleStatefulRequest()
#30 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Session\\Middleware\\StartSession->handle()
#31 /var/www/main/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/AddQueuedCookiesToResponse.php(37): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#32 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Cookie\\Middleware\\AddQueuedCookiesToResponse->handle()
#33 /var/www/main/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/EncryptCookies.php(67): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#34 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Cookie\\Middleware\\EncryptCookies->handle()
#35 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(116): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#36 /var/www/main/vendor/laravel/framework/src/Illuminate/Routing/Router.php(726): Illuminate\\Pipeline\\Pipeline->then()
#37 /var/www/main/vendor/laravel/framework/src/Illuminate/Routing/Router.php(703): Illuminate\\Routing\\Router->runRouteWithinStack()
#38 /var/www/main/vendor/laravel/framework/src/Illuminate/Routing/Router.php(667): Illuminate\\Routing\\Router->runRoute()
#39 /var/www/main/vendor/laravel/framework/src/Illuminate/Routing/Router.php(656): Illuminate\\Routing\\Router->dispatchToRoute()
#40 /var/www/main/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(167): Illuminate\\Routing\\Router->dispatch()
#41 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(141): Illuminate\\Foundation\\Http\\Kernel->Illuminate\\Foundation\\Http\\{closure}()
#42 /var/www/main/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(21): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#43 /var/www/main/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/ConvertEmptyStringsToNull.php(31): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle()
#44 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Foundation\\Http\\Middleware\\ConvertEmptyStringsToNull->handle()
#45 /var/www/main/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(21): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#46 /var/www/main/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TrimStrings.php(40): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle()
#47 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Foundation\\Http\\Middleware\\TrimStrings->handle()
#48 /var/www/main/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/ValidatePostSize.php(27): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#49 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Foundation\\Http\\Middleware\\ValidatePostSize->handle()
#50 /var/www/main/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/PreventRequestsDuringMaintenance.php(86): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#51 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Foundation\\Http\\Middleware\\PreventRequestsDuringMaintenance->handle()
#52 /var/www/main/vendor/laravel/framework/src/Illuminate/Http/Middleware/TrustProxies.php(39): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#53 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Http\\Middleware\\TrustProxies->handle()
#54 /var/www/main/vendor/fruitcake/laravel-cors/src/HandleCors.php(52): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#55 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Fruitcake\\Cors\\HandleCors->handle()
#56 /var/www/main/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(116): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#57 /var/www/main/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(142): Illuminate\\Pipeline\\Pipeline->then()
#58 /var/www/main/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(111): Illuminate\\Foundation\\Http\\Kernel->sendRequestThroughRouter()
#59 /var/www/main/public/index.php(52): Illuminate\\Foundation\\Http\\Kernel->handle()
#60 {main}
"}
答案：在将电子邮件地址发送到 Mailgun 之前，我没有验证该地址。