When SMTP settings are empty, there should be a specific error message instead of a generic error. #6912

• ABP Framework version: v6.0.3
• UI Type: Angular
• Database System: EF Core (SQL Server, PostgreSQL)
• Tiered (for MVC) or Auth Server Separated (for Angular): yes
• Exception message and full stack trace:

[16:42:16 INF] 172.21.20.10 http localhost GET /api/account/profile-picture/7d69a3a9-768a-7303-1246-3a10999a1ca9 responded 200 in 268.5780 ms
[16:42:28 ERR] ---------- RemoteServiceErrorInfo ----------
{
  "code": null,
  "message": "An internal error occurred during your request!",
  "details": null,
  "data": {},
  "validationErrors": null
}

[16:42:28 ERR] Failure sending mail.
System.Net.Mail.SmtpException: Failure sending mail.
 ---> System.Net.Sockets.SocketException (10061): No connection could be made because the target machine actively refused it.
   at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.ThrowException(SocketError error, CancellationToken cancellationToken)
   at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.System.Threading.Tasks.Sources.IValueTaskSource.GetResult(Int16 token)
   at System.Threading.Tasks.ValueTask.ValueTaskSourceAsTask.<>c.<.cctor>b__4_0(Object state)
--- End of stack trace from previous location ---
   at System.Threading.Tasks.TaskToApm.End(IAsyncResult asyncResult)
   at System.Net.Sockets.TcpClient.EndConnect(IAsyncResult asyncResult)
   at System.Net.Mail.SmtpConnection.ConnectAndHandshakeAsyncResult.InitializeConnectionCallback(IAsyncResult result)
--- End of stack trace from previous location ---
   at System.Net.Mail.SmtpConnection.ConnectAndHandshakeAsyncResult.End(IAsyncResult result)
   at System.Net.Mail.SmtpClient.ConnectCallback(IAsyncResult result)
   --- End of inner exception stack trace ---
   at Volo.Abp.Emailing.Smtp.SmtpEmailSender.SendEmailAsync(MailMessage mail)
   at Volo.Abp.Emailing.EmailSenderBase.SendAsync(MailMessage mail, Boolean normalize)
   at Volo.Abp.Emailing.EmailSenderBase.SendAsync(String to, String subject, String body, Boolean isBodyHtml)
   at Volo.Abp.Account.Emailing.AccountEmailer.SendEmailConfirmationLinkAsync(IdentityUser user, String confirmationToken, String appName, String returnUrl, String returnUrlHash)
   at Volo.Abp.Account.AccountAppService.SendEmailConfirmationTokenAsync(IdentityUser user, String applicationName, String returnUrl, String returnUrlHash)
   at Volo.Abp.Account.AccountAppService.SendEmailConfirmationTokenAsync(SendEmailConfirmationTokenDto input)
   at Castle.DynamicProxy.AsyncInterceptorBase.ProceedAsynchronous(IInvocation invocation, IInvocationProceedInfo proceedInfo)
   at Volo.Abp.Castle.DynamicProxy.CastleAbpMethodInvocationAdapter.ProceedAsync()
   at Volo.Abp.Authorization.AuthorizationInterceptor.InterceptAsync(IAbpMethodInvocation invocation)
   at Volo.Abp.Castle.DynamicProxy.CastleAsyncAbpInterceptorAdapter`1.InterceptAsync(IInvocation invocation, IInvocationProceedInfo proceedInfo, Func`3 proceed)
   at Castle.DynamicProxy.AsyncInterceptorBase.ProceedAsynchronous(IInvocation invocation, IInvocationProceedInfo proceedInfo)
   at Volo.Abp.Castle.DynamicProxy.CastleAbpMethodInvocationAdapter.ProceedAsync()
   at Volo.Abp.GlobalFeatures.GlobalFeatureInterceptor.InterceptAsync(IAbpMethodInvocation invocation)
   at Volo.Abp.Castle.DynamicProxy.CastleAsyncAbpInterceptorAdapter`1.InterceptAsync(IInvocation invocation, IInvocationProceedInfo proceedInfo, Func`3 proceed)
   at Castle.DynamicProxy.AsyncInterceptorBase.ProceedAsynchronous(IInvocation invocation, IInvocationProceedInfo proceedInfo)
   at Volo.Abp.Castle.DynamicProxy.CastleAbpMethodInvocationAdapter.ProceedAsync()
   at Volo.Abp.Auditing.AuditingInterceptor.ProceedByLoggingAsync(IAbpMethodInvocation invocation, IAuditingHelper auditingHelper, IAuditLogScope auditLogScope)
   at Volo.Abp.Auditing.AuditingInterceptor.InterceptAsync(IAbpMethodInvocation invocation)
   at Volo.Abp.Castle.DynamicProxy.CastleAsyncAbpInterceptorAdapter`1.InterceptAsync(IInvocation invocation, IInvocationProceedInfo proceedInfo, Func`3 proceed)
   at Castle.DynamicProxy.AsyncInterceptorBase.ProceedAsynchronous(IInvocation invocation, IInvocationProceedInfo proceedInfo)
   at Volo.Abp.Castle.DynamicProxy.CastleAbpMethodInvocationAdapter.ProceedAsync()
   at Volo.Abp.Validation.ValidationInterceptor.InterceptAsync(IAbpMethodInvocation invocation)
   at Volo.Abp.Castle.DynamicProxy.CastleAsyncAbpInterceptorAdapter`1.InterceptAsync(IInvocation invocation, IInvocationProceedInfo proceedInfo, Func`3 proceed)
   at Castle.DynamicProxy.AsyncInterceptorBase.ProceedAsynchronous(IInvocation invocation, IInvocationProceedInfo proceedInfo)
   at Volo.Abp.Castle.DynamicProxy.CastleAbpMethodInvocationAdapter.ProceedAsync()
   at Volo.Abp.Uow.UnitOfWorkInterceptor.InterceptAsync(IAbpMethodInvocation invocation)
   at Volo.Abp.Castle.DynamicProxy.CastleAsyncAbpInterceptorAdapter`1.InterceptAsync(IInvocation invocation, IInvocationProceedInfo proceedInfo, Func`3 proceed)
   at lambda_method4052(Closure , Object )
   at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.AwaitableResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Logged|12_1(ControllerActionInvoker invoker)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextExceptionFilterAsync>g__Awaited|26_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
[16:42:28 ERR] 172.21.20.10 http localhost POST /api/account/send-email-confirmation-token responded 500 in 5346.7778 ms

• Steps to reproduce the issue:

1. Make sure SMTP settings are empty
2. Login with the default or host user
3. click on the My Account tab on the right upper side of the screen
4. Click on the personal info tab
5. Enter the email information and press verify
6. "An internal error occurred during your request" popup appears on the screen

• Expected outcome: There should be a specific error message instead of a generic error message.