The following global MTA settings can be configured.
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Enable authentication |
Enables SMTP client authentication so users can authenticate. Only authenticated users or users from trusted networks are allowed to relay mail.
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TLS authentication only |
When checked, forces all SMTP auth to use Transaction Level Security (similar to SSL) to avoid passing passwords in the clear.
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Web mail MTA Hostname |
MTA that the web server connects to for sending mail.
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Web mail MTA port |
The default is port 25. This cannot be changed from the administration console.
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MTA Trusted Networks |
This is a network where mail is relayed arbitrarily. In general MTAs must not relay mail to addresses they do not service. This creates an exception to that rule.
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Relay MTA for external delivery |
External MTA (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.
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Maximum message size |
This is the maximum size for a message and it's attachments to be received. The default is 10000 kb.
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Maximum size of an uploaded |
This is the maximum size of a single attachment.
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Enable DNS lookups |
The Zimbra MTA makes an explicit DNS query for the MX record of the recipient domain. The default is enabled. If this option is disabled, set a relay host in the Relay MTA for external delivery field.
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Protocol checks |
These fields can be checked to reject unsolicited commercial email for more SPAM control.
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DNS checks |
These fields can be checked to reject mail, if the client's IP address is unknown, the hostname in the greeting is unknown, and/or if the sender's domain is unknown.
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Add X-Originating-IP to messages |
This is enabled by default. Every email sent directly from the server includes the X-Originating-IP in the message header. This is the IP address of the host of the sender.
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