Changing the MTA Configuration for Servers

Authentication

• Authentication should be enabled, to support mobile SMTP authentication users so that their email client can talk to the Zimbra MTA.

• TLS authentication only forces all SMTP auth to use Transaction Level Security (similar to SSL) to avoid passing passwords in the clear.

Network

• Web mail MTA Host name and Web mail MTA Port. The MTA that the web server connects to for sending mail. The default port number is 25.

• Relay MTA for external delivery. (e.g., the ISP requires that all mail originating from your network be relayed through their MTA) to which the Zimbra Postfix relays non-local email. See Relay MTA for external delivery.

• MTA Trusted Networks. Trusted networks that are allowed to relay mail can be configured. Before setting trusted networks for a server, make sure that MTA trusted networks have been set up in the global settings.

• If Enable DNS lookups is checked, the Zimbra MTA makes an explicit DNS query for the MX record of the recipient domain. If this option is disabled, set a relay host in the Relay MTA for external delivery.

Milter Server

• If Enable Milter Server is checked, the milter enforces the rules that are set p for who can send email to a distribution list.