Hi @Peter MacEwen ,
Welcome to our forum!
What's the version of your Outlook 2019? (File > Office Account > About Outlook). Please make sure you have upgraded your Outlook to the latest version.
And does this issue occur with other clients?
Based on my experience, when Outlook crash, it's suggested that you could try the following steps to troubleshoot in this article:
If the above doesn't help, based on my research on the error you provided, I found an article introduced that the similar error may be related to a registry. For more information, please refer to: How to disable 'Block signing into Office' policy in Office 365?
(Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information. And serious problems can occur if you modify the registry incorrectly. Before making changes, back up the registry to restore it in case something goes wrong.)
Hope the above help!
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