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Please kindly understand that the Outlook tag here we mainly focus on general issues about Outlook desktop client. If your account type is a personal account (outlook.com), it's suggested that you could post your case in dedicated forum for Outlook.com for more professional advice.
As far as I know, the login address for personal and organizational accounts cannot be changed. It's by design. More information, see: How to sign in to Outlook on the web - Microsoft Support.
For personal accounts, please log in: https://outlook.live.com/.
For an organization account, please log in: https://outlook.office.com/.
Hope this helps!
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