Using classic Outlook for Windows in business environments
Thank you for reaching out to the Microsoft Q&A Forum.
Based on your description, this error may indicate that the Outlook profile is missing or contains incorrect Microsoft Exchange configuration information, preventing Classic Outlook from connecting to your mailbox.
As a first step, I recommend creating a new Outlook profile by following the instructions in the article below:
Create an Outlook profile | Microsoft Support
After creating the new profile, set it as the default profile and then open Classic Outlook again.
Please let me know how it goes.
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