function Analysis of Postfix, Dovecot, SquirrelMail, MySQL, AMaVis, Clam Antivirus and spamassasin in mail reception

Tutorials for reference URLs: https://workaround.org/ispmail/lenny/bigpicture
the function distribution process of each software in the mail receiving processIn the process of sending and receiving e-mails, the Postfix, Dovecot, SquirrelMail, MySQL, AMaVis, Clam Antivirus, and Spamassasin functional classification flowcharts are as follows:

2. E-Mail uses the SMTP protocol to enter the mail server over TCP port 25. Postfix monitors this port, receives e-mails and carries out some basic checks. These checks such as: is the sender on the blacklist? is the message certified and no subsequent checks are required? Or, the message is sent to an invalid user of the system? If the sender is not a pedestrian, you can set a tag for the message. In this step, postfix can choose to refuse to receive mail or receive mail.
4. After receiving the message, Postfix uses the SMTP protocol to forward TCP port 10024 to AMAVis for content detection. Note that after this step, you cannot continue to refuse to receive e-mail messages. Therefore, Amavis can only take a message or discard it. Usually AMaVis will add tags to the message so that the user knows if AMaVis thinks the message is spam.
6. AMaVis Let Spamassasin check if the message is junk mail. It can improve the accuracy of spamassasin to discriminate spam by setting the spamassasin of spam messages.
8. Amavis also runs CLAMAV detection message to see if the message contains a virus
10. After the check is complete, the AMAVis is sent back to Postfix via the TCP 10025 port. Postfix is configured to trust messages received from this port, so no further detection of the message is possible.
12. After that, postfix the mail to Dovecot. Dovecot, you can pre-design your mail acceptance rules so that messages can be stored in a specific folder
14. Dovecot storing messages to the hard disk in Maildir format
16. Users ' mail clients can view messages through the POP3 protocol and the IMAP protocol

function Analysis of Postfix, Dovecot, SquirrelMail, MySQL, AMaVis, Clam Antivirus and spamassasin in mail reception