Missing email on Xbox

You might look on this page to find ways to find out your email:

Find your Microsoft account email address

I guess in your case the ways to find out the email are to view it on your Xbox if you're still logged in on the account or use your phone number to log in if you have previously added it to the account.

Hello Panda.2,

I would suggest contacting an Xbox Live support agent by following the steps below. The agent would be able to search for your account by looking up your credit / debit cards that are associated with your account or your Gamertag.
Hopefully when they send the security (fortify) code to your phone number or emails.. you'll receive them and they'll be able to tell you what you're Microsoft email is.

As provided above the best way to reach Live Support would be here:
https://support.xbox.com/contact-us#0



Step 1 ----Select Xbox One

Step 2 ----Select See other options

Step 3 ----Select topic (Ex. System Update)

Step 4 ----Select "Show contact options"

Step 5 ----Select request a call from support



I hope this helps a bit more.

Felix

Xbox forums support

You might need to fill out the account recovery form as well.

https://support.microsoft.com/en-us/help/17875/microsoft-account-recover

You will need the email address. You can contact
Xbox Support for assistance with it if you need to.

One email must be missing, as you can't make a second Xbox account on the same email