Enhance Guest Invite authentication to recognize disabled aliases under a Microsoft account
Microsoft Teams Guest invites should work for any email address that belongs to a Microsoft account, regardless of whether or not that email address is an active / primary alias for the account.
I recently received a guest invite from a former employer on my personal email address. The email address that recieved this remains my primary email, but i disabled it as a login alias to stop hackers from trying to breach my account. As a result, I am unable to accept the Teams guest invitation, as this email address is not an active alias, despite the fact that the invited email account falls under my account. Many Microsoft users maintain legacy email addresses that almost certainly face a persistent stream of malicious login attempts; users should not have to choose between abandoning longstanding email addresses and leaving them open to potential compromise.
In my own case, I removed my primary email address as a Microsoft alias after 20 years of use and inclusion in multiple breaches. When my email was compromised by a hacked Microsoft support account (https://www.zdnet.com/article/microsoft-discloses-security-breach-impacting-some-outlook-accounts/) I saw persistent login attempts using this alias in my security history, so I disabled it to stop these.