Thanks for your prompt reply, Upackage.

May I know what email provider is connected to your QuickBooks Desktop account? In the meantime, let's make sure that your QuickBooks Desktop is updated to the latest release.

Then, try to check if the email greeting reverts back to the default. If you're still getting the same result, we can do the Verify and Rebuild Data. This might be caused by a damaged company file. 

You can follow the steps in this article: Verify and Rebuild Data in QuickBooks Desktop.

In case you need more help in completing other tasks in QuickBooks, you can check our guides here.

Please let me know how it goes. I'll be around to help you out some more. Stay safe!