Hi @valtrqr ,
Does the problem only occur on a specific client? What is the detailed version of Outlook (File > Office Account > About Outlook) Please make sure that you have upgraded it to the latest version. (File > Office Account > Update Options > Update Now)
Have you recently changed the password? If so, remove the old credential and create a new profile from control panel then re-add your account.
- Remove the old credential: From Control Panel on the computer, search for Credential Manager, choose Windows Credentials, select the exchange account.
- Create a new profile: Go to Control Panel > Mail > Show Profiles > Add, re-connect the account.
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