What is ETRN?

Question

What is ETRN and how do I set it up in GMS Mail?

Answer

ETRN (Extended Turn) is an extension to the Simple Mail Transfer Protocol that allows an SMTP server to send a request to another SMTP server to send any e-mail messages it has.

The ETRN command has been specifically designed to allow intergration with dial-up mail servers. A dial-up mail server can connect to the Gordano GMS Mail server and issue the ETRN command to force all the e-mail for its server to be posted out.

The extended ETRN command is issued by the client host when it wishes to start the SMTP queue processing of a given server host.

The ETRN command may be issued at any time once a session is established, as long as there is not a transaction occuring. Thus, this command is illegal between a MAIL FROM: command and the end of the DATA commands and responses.

The syntax of this command can be as simple as…

ETRN node_name

The specified node name must be a fully qualified domain name for the node, which may refer to a CNAME or MX pointer in the DNS.

Since the processing of the queues may take some time, this command should return immediately with a response to the client host.

The valid return codes for this command are:

250 OK, queuing for node  started
251 OK, no messages waiting for node 
252 OK, pending messages for node  started
253 OK,  pending messages for node  started
458 Unable to queue messages for node 
459 Node  not allowed: 
500 Syntax Error
501 Syntax Error in Parameters

ETRN by itself is not a completely secure command so the ETRN utility additionally provides the capability of password protecting mail queues.
If no password is given then NTMail will only deliver to an MX record.
IF a plaintext password is given we will deliver to MX and/or a static IP address.
If an MD5 password is given then we will deliver to MX and any (dynamic) IP.

For a more detailed description of ETRN, view RFC1985.

See Also:

• How do I get #GMS# to request email using the ETRN extension?
• What options can other servers use to request email using the ETRN extension?

Keywords:ETRN AllowETRN Dialup NTMAIL