Global MTA Settings

The Global Settings>MTA page is used to enable or disable authentication and configure a relay hostname, the maximum message size, enable DNS lookup, protocol checks, and DNS checks.

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 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.

The Relay MTA for external delivery is the relay host name. This is the Zimbra MTA to which Postfix relays non-local email.

If your MX records point to a spam-relay or any other external non-Zimbra server, enter the name of that server in the Inbound SMTP host name field. This check compares the domain MX setting against the zimbraInboundSmtpHostname setting, if set. If this attribute is not set, the domain MX setting is checked against zimbraSmtpHostname.

MTA Trusted Networks. Configure trusted networks that are allowed to relay mail. Specify a list of network addresses, separated by commas and/or a space.

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.

If Allow domain administrators to check MX records from Admin Console is checked, domain administrators can check the MX records for their domain.

Milter Server

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

Archiving Configuration

If you installed the Archiving feature, you can enable it here.

Messages

Set the Maximum messages size for a message and it’s attachments that can be sent. Note: To set the maximum size of an uploaded file to Briefcase, go to the General Information page.

You can enable the X-Originating-IP header to messages checkbox. The X-Originating-IP header information specifies the original sending IP of the email message the server is forwarding.

Policy Service Checks

Customize zimbraMtaRestriction (restrictions to reject some suspect SMTP clients).

Protocol checks

To reject unsolicited commercial email (UCE), for spam control.

DNS checks

To reject mail if the client’s IP address is unknown, the hostname in the greeting is unknown, or if the sender’s domain is unknown.

Add other email recipient restrictions to the List of RBLs field.

Note:

RBL (Real time black-hole lists) can be turned on or off from the Zimbra CLI. See the section Adding RBLs using the CLI on page 47.