,-------------------------.                                                    
                                                                                   |MTA                      |                                                    
                                                                                   |-------------------------|                                                    
                                                                                   |(Mail Transport Agent)   |                                                    
                                                                                   |andere SMTP-Server       |                                                    
                                                                                   |im Internet bzw. Intranet|                                                    
                                                                                   |TCP/IP - Port 25         |                                                    
                                                                                   `-------------------------'                                                    
                                                                                                |                                                                 
                                                                                                |                                                                 
                                                                                    ,----------------------.   ,-----------------.                                
                                                                                    |smtpd:25              |   |smtpd:10024      |                                
                                                                                    |----------------------|   |-----------------|                                
                                                                                    |SMTP-Daemon           |---|SMTP-Daemon      |                                
                                                                                    |TCP/IP Port 25        |   |TCP/IP Port 10024|                                
                                                                                    |mit smtpd_proxy_filter|   `-----------------'                                
                                                                                    `----------------------'             |                                        
                             -------------------------------------------------------------------------------             |                                        
,-------------------------.  ,----------------------------.                           ,--------------------.             |                                        
|smtpd:10025              |  |Postfix                     |   ,-------------------.   |Spamassassin        |   ,-----------------.   ,---------------------------.
|-------------------------|  |----------------------------|   |IMAP-Server        |   |--------------------|   |AMaViS           |   |Entpacker                  |
|SMTP-Daemon              |  |weitere Be-/Abarbeitung     |   |-------------------|   |Backend-System zum  |   |-----------------|   |---------------------------|
|TCP/IP Port 10025        |--|der eMail durch den         |---|Mail-Delivery-Agent|   |Prüfen der eMail auf|   |Master Prozess   |   |Backend-System zum         |
|*ohne* smtpd_proxy_filter|  |Mail-Transport-Agent Postfix|   |Dovecot IMAP-Server|   |unerwünschte Inhalte|   |(Frontend-System)|   |Entpacken von Dateianhängen|
`-------------------------'  `----------------------------'   `-------------------'   `--------------------'   `-----------------'   `---------------------------'
                                                                                                                                                                  
                                                                                                                                                                  
                                                                                                            ,------------------------.                            
                                                                                                            |Virenscanner            |                            
                                                                                                            |------------------------|                            
                                                                                                            |Backend-System zum      |                            
                                                                                                            |Prüfen der eMail und der|                            
                                                                                                            |Anhänge auf Schadcode   |                            
                                                                                                            `------------------------'