Outlook cannot open the file because it is not associated with the default identity

Spotlight may display mail messages as part of a search result but Outlook for Mac may present the following error when attempting to open them:

Outlook cannot open the file because it is not associated with the default identity.

This problem occurs when Spotlight returns mail messages from an identity other than that which is currently set as the default for Outlook. Quite often these unassociated messages are from identities abandoned while troubleshooting an . . .

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