copy address from email search window
When you search for an email address in the OSX Mail search bar, if you select the address from the dropdown, the mail app will automatically add the option From: in front of the email address in the search bar. Thus, the mail messages that show up in the left mail list will change so that only emails from the selected email address are displayed.

If you do not have any messages that are actually From: the email address selected, no emails will be displayed in the list. You may need to change the From: option in the search bar to Entire Message in order to see messages where a certain email address was CC'ed or if it was written in the email message text.