Should we check mails in Spam of public emails such as Google and Yahoo?

Yes, off course. We should check the emails in Spam. Why? When the private email users send mail to the free or public email users such as Google and Yahoo, the unknown emails will be stored in Spam / Junk (that is security policy of public emails). At that time, open the email and click "Report not spam". After doing that, the emails from a private email user you've reported as "Not Spam" will be stored in Inbox. But checking the emails in Spam is the good habit for the public email users. I write this post because some public email users such as Google and Yahoo are missing the important mails from the private email users.

Thank you.