Email filtering output is capable of affecting messages.
Email filtering . Most often this refers to the automatic processing of incoming messages , but the term also applies to the intervention of human intelligence in addition to anti-spam techniques , and to outgoing emails as well as those being received . For its output , it might pass the message through unchanged for delivery to the user 's mailbox , redirect the message for delivery elsewhere , or even throw the message away . Some mail filters are able to edit messages during processing .