Hi @TRDx2 ,
I tried a lot of tests in my environment but could not stop this behavior.
Is this Auto forward behavior really necessary?
If you were intended to delegate User A's email messages and calendars. As a workaround, it would be more suggested for you to grant the full access permission of User A to User B. So that User A's emails will not influence User B and User B can still delegate User A's email messages simply in Outlook desktop client like below:
Manage permissions for recipients
Hope this can be helpful.
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