Microsoft discontinues linked accounts in Outlook.com due to security concern
Linked accounts was a big convenience because it allowed you to switch between different email accounts without having to keeping re-entering your user name and password. However, if one account was compromised, all of them were - and that's not a good thing.
In July, this feature will be discontinued and replaced with email aliases, which will let you use alternative email addresses that use the same inbox, contacts, etc. as your primary account. All aliases will have the same password (which does make it easier to remember) and you get up to ten. You can also forward mail from a different account to your primary account or send mail from another account.
Find out more here: