X-OWA-Error: Microsoft.Exchange.Security.Authentication.TokenMungingException

Scenario:  When a user tries to access OWA, the receive the following error:

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X-OWA-Error: Microsoft.Exchange.Security.Authentication.TokenMungingException

Resolution: This is the result of the mailbox being a 'linked mailbox' and having a value in the 'linked master account'.

Run the following to view the value:
get-user batman15 | select linkedmasteraccount

Run the following to remove the value:
set-user batman15 -linkedmasteraccount $null