When you move from one Microsoft Exchange service to another, such as from an internal Exchange server to Office365, and you want to keep your current profile, you cannot remove the original Exchange account from your profile.
Logically, making the new email account and associated data file the default should work, but changing the defaults doesn’t change the primary or primary account.
Primary Exchange Account
The main Exchange account is the first account to be added to the profile. The primary account cannot be removed from a profile until all other Exchange accounts have been removed from the profile (when the primary account is removed, the next Exchange account added will be considered the primary account).
All other Exchange accounts added to a profile are considered child accounts.
The recommended method for changing the primary account is to recreate the user profile and add the correct account first. However, there are two other options: edit the registry and then remove the main Exchange account from your profile or add a pst file to the profile, set it as the default and then remove the Exchange accounts.
Removing the Primary Account
You have three options when you need to remove a main account from your profile. You can create a new profile (recommended), remove all Exchange accounts from your profile, and then re-add the new account or remove a registry key so that you can remove the main account from the registry.
While creating a new profile can be faster (and is the recommended method), there is a complicated method you can use to change the main account and maintain the profile, while preserving the specific profile settings.
- Go to Control Panel, Mail, and remove all Exchange accounts from the profile, removing the main account last. You will need to add a pst to the profile and set it as the default data file, then restart Outlook.
- Close Outlook and go back to the Control Panel, Mail applet and add the new account. (In my experience, the new account may not appear in the list until I restart Outlook.)
- Restart Outlook. Go to account settings and set * .ost as default. You will need to restart Outlook one more time to remove the *.pst from your profile.
I said it was complicated, although not bad if you only have a few Exchange accounts…if you have a lot of Exchange accounts or if the mailboxes you store in the profile are huge, you can edit the registry to get the ‘ head ‘mark’ and then delete the account. Editing the registry is generally the best option if it takes a long time to resync mailboxes (or if you have a metered connection) or if you have many Exchange accounts in your profile.
Remove the primary account by editing the registry
You can edit the record to remove the primary assignment; However, Microsoft does not support or recommend it. If you make a mistake, you must create a new profile, restore the profile key you exported, or use System Restore to revert to an earlier restore point.
Close Outlook and open the registry editor.
Press Windows Key + R to open the Run command, then type regedit in the Run field and press Enter.
To remove the Outlook 2010 master account from the registry, locate the profile key:
HKEY_CURRENT_USER\Software\Microsoft\Windows NT\Current Version\Windows Messaging Subsystem\Profile\profile name
Export the profile key and then locate and delete one (or both) registry keys related to the main account.
I searched for 001f662b in the profile (or 001f6641 in Outlook 2016) because every account uses this value. You will find two keys for each account that contain this value and you must delete the second key associated with the main account (you can delete both keys). Once I did this I was able to remove the main account from the profile.
To verify this is the correct account, look at the alias in 001e660b (the alias is at the end of the data: /o=ExchangeLabs/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=74479d8714d3414c8502650cc962e1c6- maryc) or double click on other keys and find the address. For example, in the screenshot below, the address is in 001f6641.
Note: You must delete the entire key (on the left), not just the registry value. The value will help you find the correct key to delete.
In the current versions of Outlook 2016/2019 / Outlook 365 (subscription), you have no visual cues to identify the account. Search for 001f6641 and delete the first entry found, after verifying that the key belongs to the master account. Try to remove the account from the profile (in Control Panel, Mail), if it doesn’t work, find the following key for the address and try again. (There are at least 3 keys for each Exchange account in the latest versions.)