MSExchangeMailboxAssistants event 4999

Максим Хирьянов 96 Reputation points

MS Windows 2019, MS Exchange 2019 CU7

MS Windows and MS Exchange are installed with Russian. An attempt was made to switch the Windows interface to English, after which the MSExchangeMailboxAssistants service starts with an error and stops. I tried to return the Windows interface language back to Russian, but the service error remained.

Thanks for any help.

Error text:
Watson report about to be sent for process id: 26956, with parameters: E12IIS, c-RTL-AMD64, 15.02.0721.008, MSExchangeMailboxAssistants, M.Exchange.Assistants, M.E.A.AssistantsRpcServer.RegisterAssistant, System.ArgumentException, 503a-dumptidset, 15.02.0721.008.
ErrorReportingEnabled: False

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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Accepted answer
  1. Максим Хирьянов 96 Reputation points

    Everything was decided by installing CU8. The service MSExchangeMailboxAssistants is working normally, there are no errors.

1 additional answer

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  1. Lucas Liu-MSFT 6,106 Reputation points

    Hi @Максим Хирьянов ,
    Are there any Exchange functions that are not working properly?
    Does any specific error pop up when you start the MS Exchange Mailbox Assistant service?
    Do you try to restart the Exchange server and MSExchange Mailbox Assistants service? If not, please try.
    1.1.Please run the following command to make sure that all required service are running:


    2.According to the error information, we could only know that Microsoft Exchange Assistants service failed. It may not be possible to know the root cause of the error, so please check if there are any related errors in the event log, or if there are any errors in Exchange. Please share the information with us, but please pay attention to covering your personal information.

    If the response is helpful, please click "Accept Answer" and upvote it.
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