Inbox were and save box where?

For instance inbox of you@gmail.com and save on the local folders account.

Hi Matt, As e-mails come in, they are sorted into a box named "save" [that holds e-mails addresses that I know]. Some e-mails are directed to a box named "spam." All other e-mails show up in a box entitled "in" [containing unknown e-mail addresses]. Sometimes I want to save an unknown e-mail from the "in" box. For years I have been able to highlight the address of the unknown e-mail and drag and drop it into my "save" box and it remains there. I can also then register that unknown address so that in the future it automatically is directed to my "save" box. About 2 months ago, when I dragged an unknown e-mail address [from "in"] to the "save" box, it completely disappeared. I couldn't find it anywhere. [It did not go to spam nor to trash.] I thought that I had too many stored e-mails. So, I deleted a lot of e-mails and also transferred a lot of e-mails to my local folders. But that didn't help at all. Do you have any ideas?