Whenever an e-mail has been flagged as spam by our systems, it will be rejected. That means our server will deny accepting the e-mail message and the system at the other end (the client) will issue a delivery failure notice to the sender (the message „bounces“). So, the sender will be notified by their own provider if there was a problem with delivering the message. It is the same bounce mechanism commonly in place to deal with situations where someone tries to send an e-mail to an address that doesn't exist, for instance when there has been a spelling mistake.
The setup has mainly two sections:
(1) shows the options for filtering at protocol level. Filtering is done before the server "sees" the real message.
(2) is the area of content filtering. Filtering is done by various techniques, which check for known patterns in the e-mail. You may choose, whether detected spam should get rejected or get moved into the "Junk"-folder for instance.
Important: The options in area 1 and also the option for blocking executable attachments will always reject messages (except greylisting, this only rejects temporary), if a message matches there (independantly of the settings in area 2).
Spam protection through greylisting