The Outlook Change Notifier add-in installed by iTunes may also be to blame for the autocomplete bug. Check whether the problem still exists after disabling it using the instructions below:

1. To access the Add-Ins tab, open Outlook and go to File > Options > Add-Ins.
2. Next to the Manage COM add-ins option, press the Go button.
3. Locate the Outlook Change Notifier add-in in the Add-ins dialogue window and uncheck it.
4. Then, to confirm, click OK, and then return to the main window.

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