@ta5656 Unfortunately, normal users doesn't have an option to update the username but the community support team can do. The only way to get it updated is by sending an email to the community support or admin and they will change it for you.
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You cannot change to outlook as only work/organizational accounts are allowed post SSO.
Changing email is not an option.
However, when you change jobs / tenant, you need to register with the Community using that new email address and share with us the profile URL. We will then map your current community profile to your new email address. You will not lose any of your contributions in this process.