why outlook has access denied with dcomcnfg identity setting to specific user

Question

Im wrote my own service-application to send entries into the calendar from outlook. In general, this is working well since 10 years.

The only thing i have to do was in dcomcfng, selecting the outlook message object, an change the running identity to an specific user and he has installed/configured outlook correctly. Everthing works fine as service.

Now my problem... :-)

A customer has become some new computer, and setting up outlook correctly. Now im going to dcomcnfg, change the identity from interactiv to that specific user. But on execution, my service had no rights(access denied) for that outlook-object.

Now i'm logged in into windows with this specific user (user : "Work101") Then i start an test-application, as normal exe file (not as service) and i receive the same error. Access deniend

If i change the identity in dcom to "interactive user", my test-application works fine. (which is User Work101)

If i change the identity in dcom to "executing user", my test-application works fine. (which is User Work101)

But if i set this user "work101" in dcom identity as specific user, i got "access denied". There is no other user like this, no writing misstake, no password misstakes...everthing is written correct.

Does someone know where is the problem, that the speicific user has no access, but the same user works fine if the identity is set to "interactive user" or "executing user" ?

I checked registry, repair office 365, restarting machine and and and. nothing works.

on my virtual machine i setting up the same type of windows, installing office, changed dcom and it runs without problem.

i dont get it -.-

the Test-app was written with direct calling the outlook.application, and also tryed with interop-functions. there was no difference on this strange computer.

@edit

- <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
- <System>
  <Provider Name="Microsoft-Windows-DistributedCOM" Guid="{1B562E86-B7AA-4131-BADC-B6F3A001407E}" EventSourceName="DCOM" /> 
  <EventID Qualifiers="0">10000</EventID> 
  <Version>0</Version> 
  <Level>2</Level> 
  <Task>0</Task> 
  <Opcode>0</Opcode> 
  <Keywords>0x8080000000000000</Keywords> 
  <TimeCreated SystemTime="2023-08-21T14:06:47.3753088Z" /> 
  <EventRecordID>22884</EventRecordID> 
  <Correlation ActivityID="{7c7f596d-3cd3-4cba-892b-8f6c7524d954}" /> 
  <Execution ProcessID="976" ThreadID="16368" /> 
  <Channel>System</Channel> 
  <Computer>VS-ADS02</Computer> 
  <Security UserID="S-1-5-21-3793602545-3278945853-1181855047-1630" /> 
  </System>
- <EventData>
  <Data Name="param1">C:\Program Files\Microsoft Office\Root\Office16\OUTLOOK.EXE -Embedding</Data> 
  <Data Name="param2">2147942405</Data> 
  <Data Name="param3">{0006F03A-0000-0000-C000-000000000046}</Data> 
  </EventData>
  </Event>