Using New Outlook on Windows for personal email, calendar, and contact management
Hi Matt,
The way to stop Outlook from forcing an outlook.com account is to use Outlook Classic with a fresh mail profile and add your accounts manually so autodiscover cannot switch them to outlook.com.
Close Outlook first. Open the old Control Panel > Mail > Show Profiles > Add, and give the profile a short name. When the Add Account window opens, click Advanced options and tick Let me set up my account manually. Add your work account first, next add your personal account.
If it is Gmail, choose Google and sign in. If it is an ISP mailbox, choose IMAP and enter the server names from your provider. When both are added, set Always use this profile to the one you just created and click OK.
On new and old Outlook: If your app shows a New Outlook toggle in the top right, switch it off to return to Classic. If you only have the new Outlook from the Store, install the Microsoft 365 desktop apps that include Outlook Classic using the same subscription account, then repeat the steps above in Classic.
After this, Outlook should open with the new profile and only the accounts you added.
If anything in those steps is unclear, tell me what type of personal account you have and whether your work account is Microsoft 365 or on-prem Exchange, and I will give you the exact server choices.