When you change (rename) to a new primary alias email address for your Microsoft account, you don't lose your old alias and you keep all of your data - such as your inbox, profile information, and contacts. The email address of the old primary alias will still be listed as an alias
for your Microsoft account, but just no longer the primary alias
. You can still use the old primary alias email address to sign in and send and receive mail.
It will take an hour or more for the email rename to be finalized. You will receive an email notification to the alternate email address
in your Microsoft Account profile to notify you that the change has occurred.
It might take up to 48 hours
for your new primary alias email address to appear across all devices and services. Also, some of your friends might appear offline until they sign out and sign back in.