The filtering systems used by mailbox providers have methods for classifying email as spam, email that a subscriber may not want to receive. When this occurs and the mailbox provider does not block the email, it places the email in a folder other than the inbox. Such folders may be called:
Despite its name, the folder is essentially the same.
These folders allow subscribers to view email that was not delivered to the inbox and decide whether or not they want to receive it.
Mailbox providers typically give subscribers the option to report the email with the This is Not Spam (TINS) function, which moves the email into the inbox. In doing so, subscribers help improve the sender's TINS rate. A favorable TINS rate helps the sender's overall reputation.