Administration

ETRN Tab

Purpose

ETRN defines a method of queueing mail for a mail server which does not have a permanent connection to the Internet. This is achieved by a server moving mail for specified domains into spool queues, which are released when the remote mail server informs the ETRN server that is is now on-line and ready to receive messages. i-Mail provides both the server and client sides of ETRN.

ETRN is similar to the smart POP collection that i-Mail does, except is is a 'push' mechanism where the ISP is in control if the mail sending, where with POP collect i-Mail controls the downloads.

To use ETRN the client must have a static IP address or be configured with dynamic DNS so that the ETRN server knows where to deliver the mail. Smart POP does not have this drawback.

As a client, i-Mail can connect to an ETRN server and indicate that it is on line and ready to receive data. i-Mail must have 'Allow SMTP clients' configured in the TCP Ports/Connections tab. Ask your ISP what the server and queue names are for your domain. The ETRN activators are scheduled by the inbound scheduler on the Scheduling tab.

As a server i-Mail will respond to client requests to 'despool' its queue for the domain to the specified IP or DNS address.

ETRN Queue Activators

Queue activators set up i-Mail as an ETRN client.

To add queues, press the 'Add' button and enter the SMTP server and the queue designated for your domain. You must have 'Allow SMTP clients' configured in the TCP Ports/Connections tab.

Additionally the IP bindings should be configured for either all IP addresses or your public interface, as the ETRN server you are contacting needs to be able to talk directly with i-Mail on your server.

ETRN Server Queues

Server Queues allow i-Mail to spool mail for specified domains that may not have dedicated IP connections.

To add an ETRN server queue press the 'Add' button and enter the details of the domain and a queue name to use to activate the spooler.

For the client connecting, specify the IP or DNS address of the i-Mail server as the ETRN SMTP server and use the queue name configured as the ETRN queue on the client. Now when the client connects and sends the ETRN commands, i-Mail will send any mail that has been received for that domain to the address specified.

Tips

For companies that have multiple sites and control the IP addresses between sites, ETRN can be a useful tool to route messages between mail servers without needing to worry about recipient replacement rules. In this situation set up server queues for the remote sites and then configure the remote systems to dial in upon requests to that IP address and trigger the despooler.