How to recover my Microsoft account by the Office key?

You cannot recover your Microsoft account using just an Office product key, what do you mean by you lost your Email, do you mean you are unable to remember the Microsoft account email address or is your Microsoft account inaccessible?

In the meantime, using any Microsoft account or Email address you may have, try logging into this link to check if you can find your Office licence or subscription.

https://account.microsoft.com/services/