Magic Flow not working for aliased @automattic.com email addresses

[dmallory42]

Context and steps to reproduce

As noted in #103479, an error occurs when trying to use the Magic Link flow with an aliased @automattic.com email address.

Reproduction steps:

• Go to any flow which requires Jetpack authentication (the easiest one I can think of is to go to jurassic.ninja and log out of your WP account, then click Login).
• On the login screen (see screenshot below), enter an email that isn't already associated with an account (you can use [email protected])
  
• When prompted, click create a new account.
• Enter the email address again and click continue.
• It will fail with the following error:

Anecdotally, I tested this flow in the past when working on updates to the magic flow (e.g. #95617), so there has been a regression at some point.

Site owner impact

Fewer than 20% of the total website/platform users

Severity

Minor

What other impact(s) does this issue have?

No revenue impact

If a workaround is available, please outline it here.

No response

Platform

No response