Microsoft.Exchange.WebServices.Data.ServiceResponseException: The mailbox does not have SMTP address associated with it.

[dkekesi]

When trying to find folders on an Exchange 2016 server, I get this error: System.AggregateException: One or more errors occurred. ---> Microsoft.Exchange.WebServices.Data.ServiceResponseException: The mailbox does not have SMTP address associated with it. at Microsoft.Exchange.WebServices.Data.ServiceResponse.InternalThrowIfNecessary() at Microsoft.Exchange.WebServices.Data.MultiResponseServiceRequest`1.<ExecuteAsync>d__6.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Exchange.WebServices.Data.ExchangeService.<FindFolders>d__20.MoveNext() The mailbox works, I can send mails to it. I tried to find the exception message in the code, but I couldn't. Do you know what may cause this issue?