How to restore an email alias that was deactivated

No. If a Microsoft-domain alias such as @live.com is removed from a Microsoft account, it is permanently deleted and cannot be added back or associated with any Microsoft account again.

Supported details:

• Microsoft account email addresses are aliases.
• Before removing an alias, Microsoft warns that removing a Microsoft-domain alias such as @outlook.com, @hotmail.com, or @live.com permanently deletes that address.
• If the goal is only to stop sign-in with an old alias, aliases can be blocked from sign-in instead of being removed.

References:

• Can I change the email address that is connected to my Clipchamp account? | Microsoft Support
• How to fix "This username has been turned off" error | Microsoft Support
• Email adress alias recover - Microsoft Q&A Iam remove old alias and recover old alias my account
• Email address recovery after change - Microsoft Q&A I had previously changed my email address due to extreme amount of spams and hacking attempts (data leaks). I later found out I had an apple id created using the old email address and I have no way to log into the apple id now as the verification is getting sent to the now-removed email address.
• Urgent: Accidentally deleted @hotmail alias – "Reserved Domain" error when trying to re-add - Microsoft Q&A I accidentally removed my primary email alias – "Reserved Domain" error when trying to re-add - Microsoft Q&A I accidentally removed my primary email alias (<Mod remove PII> @hotmail.com) from my Microsoft account while trying to change my sign-in preferences. Now, I am trying to add it back because I need to receive a critical verification code for a linked service (Discord).