Is there a way to find out the users by their email address on a Stack Exchange site?
I tried putting the email in the search box, but I got no results.
Any other methods?
No. A user's email address and/or OpenID information are not public information and users cannot search for them. This is not a social network, and there's not really any reason why someone would need to locate another user by email address anyways. If you do really know someone and you have some legitimate reason to know their account on a site, go ask them in person.