Zimbra mail incoming outgoing diagram
1) it is confusion term in every mail server to understand how mails are coming and going out to and from servers. see below diagram to get understand message flow in zimbra mail server.
Incoming mail flow
Outgoing mail flow
This diagram designed for 30,000 Users for more traffic in Organization.
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Master mail flow
Zimbra mail flow:- mail are come to external network to MTA and MTA hands-off these messages to MDA (Mail store).
When User send mails to External World then User use SMTP Client program (MAPI Client ) to connect with SMTP Server (MTA), Once the Authentication mechanizes done then SMTP Server Route Message to External Exchanger ( SMTP Server ). If External exchanger accepts message then Sending mechanizes done from Originating MTA .