If you no longer want to have another email account connected to Outlook.com, you can remove the connected account from Outlook.com. You only remove the connection between the other account and Outlook.com, not the email account or the email messages.
What happens to my email when I remove a connected account?
Any email messages that were imported to Outlook.com will still be there after you disconnect the email account.
Tip: Before you remove a connected account from Outlook.com, we recommend that you sign in to the account via the original email provider and make sure your email messages are there. If they are there, after you remove your account you can delete all the account's email messages from Outlook.com and you'll still have a copy of them at your email provider. If they aren't there, after you remove the connected account, you might want to archive your email messages in a folder in Outlook.com instead of deleting them.
After you remove the account from Outlook.com, you can no longer send email from that account in Outlook.com.
How to remove a connected account
At the top of the page, select Settings > View all Outlook settings.
Select Sync email.
Under Manage your connected accounts, select the account you want to remove and then select Delete .
After you remove the account from Outlook.com, you can delete email messages from the connected account.