Hi @Simon ,
Welcome to our forum!
That all works fine until they log into a PC they did not use before the upgrade.
You mean that the account after the domain name change can run normally on the PC that has not logged in before the change, right?
If so, I think it is related to the roaming profile. It is suggested that you could add your accounts in a new profile and remember to disable the Exchange mode:
- Control panel>Mail>Show Profiles…>Add…>type the name of your new profile>click OK;
- Choose Email Account, and fill in the related information about your account>click Next;
- After your email account is successfully configured, select Change account settings and click Next;
- Under Offline Settings, uncheck Use Cached Exchange Mode>click Finish;
- Back to Mail window, choose Prompt for a profile to be used.
- Restart the Outlook.
If it still doesn't work, please try to remove the old profile in control panel and check if there're any differences.
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