If you no longer want to have another email account connected to Outlook.com, you can delete the account connection. You only delete 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 disconnect 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 an email message from that account.
How to delete a connected account
On the toolbar bar, select Settings and select Connected accounts.
Tip: Outlook.com Beta users should just click Connected accounts.
Select the account you want to remove, and then click Remove .
Click Yes to confirm that you want to stop connecting to the account.
After you remove the account from Outlook.com, you can delete email messages from the connected account.