Incoming
   Mail
Recipient MDA
Spam 60%
Ham 4%
Unsure 1%
Forgeries 10%
Connection
Rejects 10%
Unsure
   65%
Reputable Senders
           15%
Block DoS
Check ID
Filter
Virus
Filter
Quarantine
Gate
Mailbox
Border Patrol MTA (Mail Transfer Agent)
Mail Distribution Agent (MDA)
[*] [**] [spam]
[ ]
[*]
[**]
[spam]
[ ]
WebMail
Server
POP3/IMAP
Server