What options can other servers use to request email using the ETRN extension?

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Answer

GMS Mail is extremely flexible and secure in the way it can handle ETRN queues. GMS Mail supports three ETRN configurations which are enabled from the Incoming>ESMTP page of the interface.

1: No Password – Deliver to MX
This option requires no password and delivers the queue to the MX record for the post server specified in your outgoing rule. The ETRN queue is set up in the following way.

  • The domain should not currently exist within GMS Mail
  • On the Outgoing>Rules page add a rule as follows
    Target Address: domain.com
    Post Server: server.domain.com
    Port: 25
    Retry: 0
    This means send all mail for domain.com to server.domain.com on port 25 but only send when requested.
    server.domain.com should have a valid A record in DNS

  • Ensure that GMS Mail will accept mail for this domain by adding domain.com to the "Allow Relay for…" section on the Security>Relay page of the interface.
  • Update the MX records for domain.dom so that mail for that domain now arrives at your GMS sever.

2: Plaintext password – deliver to MX and static IP
ETRN by itself is not a completely secure command so the ETRN utility additionally provides the capability of password protecting mail queues. The ETRN queue is set up in the following way.

  • The domain should not currently exist within GMS Mail
  • On the Outgoing>Rules page add a rule as follows
    Target Address: domain.com
    Post Server: server.domain.com
    Port: 25
    Retry: 0
    Password: your_password
    This means send all mail for domain.com to server.domain.com on port 25 but only send when an ETRN request is made using the specified password in plain text. If the password is wrong or not provided the queue will not be delivered.
    server.domain.com should have a valid A record in DNS

  • Ensure that GMS Mail will accept mail for this domain by adding domain.com to the "Allow Relay for…" section on the Security>Relay page of the interface.
  • Update the MX records for domain.dom so that mail for that domain now arrives at your GMS sever.

3: MD5 Password – deliver to MX and any IP
This option adds an extra level of security as it requires the ETRN request to be accompanied with an MD5 encrypted password before a queue will be delivered. The ETRN queue is set up in the following way.

  • The domain should not currently exist within GMS Mail
  • On the Outgoing>Rules page add a rule as follows
    Target Address: domain.com
    Post Server: *
    Port: 25
    Retry: 0
    Password: your_password
    This means send all mail for domain.com to server.domain.com on port 25 but only send when an ETRN request is made using the specified password in encrypted format. If the password is wrong or not provided the queue will not be delivered.

  • Ensure that GMS Mail will accept mail for this domain by adding domain.com to the "Allow Relay for…" section on the Security>Relay page of the interface.
  • Update the MX records for domain.dom so that mail for that domain now arrives at your GMS sever.

There is another advantage to this option as it can be configured to send the queue to any connecting machine that issues the correct ETRN commands including the encrypted password. This means that the machine issuing the ETRN command can have a dynamic IP address and doesn’t have to have a valid A record in DNS.

Note: All 3 of these options can be enabled at the same time if required.

Gordano provides a utility called ntmetrn (glmetrn on unix) which can be used on client machines to issue ETRN commands to a GMS server. Check out the see also entry below for more information.

See Also:

Keywords:ETRN, GMS Mail, Dynamic IP

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