Help Hotmail account suddenly no longer providing emails under the new outlook account.

When I changed my hotmail to outlook, i was no longer able to log in under the hotmail name. All good.  I could still receive email under hotmail and all outloo email i made a separate folder.  Was working great for months.  I think the last email that I got was about 1/5?, no junk mail, no email for the hotmail account.  So in waiting longer then 24 hours for someone to reply to me, I created a  @live.com account and then created an alias for the origianl hotmail name.  So far it's working, but what happened when it was under outlook?  When you try to do anything in outlook it says the account is not available.  I actually got a letter in the mail from someone stating mail came back as undeliverable.  I saw coded 505 or 550?  Please help it's driving me crazy.  Thank you