An email filter is a software application that runs on a POP3/IMAP mail server and monitors all incoming email messages in order to impede any unwelcome ones from reaching a specific inbox. A few instances of such email messages would be: offers for pills or money, false bank notifications or email attachments that contain malicious software sent with the idea to damage your PC. Email filters normally check the content of an email and in case they come across specific keywords or other suspicious content, they either delete the message or re-send it to the Junk/Spam folder instead of the Inbox folder. Some hosting providers combine their own filters with up-to-date databases from spam-tracking organizations, so as to guarantee higher levels of security for their customers. Such databases contain patterns, mail server IPs and other info about spam messages recently reported by these organizations.