Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
The data file is an ost - so its right- and Outlook uses the primary account name for the data file name.
I'm a little gun-shy changing my primary alias as I have this fear I wont be able to get back into Outlook at all and have no choice but to start all over and re-install Office, or worse (which seems to be the norm these days). << If you just change the primary alias, the most you'll need to do is sign in using the Outlook.com alias. DO NOT do anything more than click the make primary link!