ETRN
[/?]
[/V[+|-]]
[/E[+|-]]
[/HELO[+|-]]
[/BYIP[+|-]]
[/SRV_SUPERDOMAINS[+|-]]
[/SRV_SELF[+|-]]
[/IP6ADDR[+|-]]
[/IMPLICIT[+|-]]
[/CLIENTIP[+|-]]
[/CLIENTPORT[+|-]]
[/C]
[/D]
[/H]
myname
servers …
The ETRN command is a utility for hosts that have intermittent connections
to Internet, such as a dial-up connection over a modem, that have arranged
for their mail to be delivered elsewhere (via an MX DNS
resource record) and queued whilst they are not connected. It sends a
trigger event to the secondary SMTP Relay server where the mail is queued,
telling it that the target's SMTP Relay server is now online and ready to
accept mail.
This trigger event is an ETRN SMTP verb sent to the SMTP
Relay server. The ETRN command connects to each of the the SMTP Relay
servers specified on its command line, and sends them an ETRN
verb. The SMTP Relay server is expected to initiate queue processing in
response and deliver any mail destined for the named host, domain, or
channel.
The use of the ETRN command will vary according to how the dial-up connection works. Usually an ETRN command, with the name of one's ISP's mailhost as an argument, is placed in a REXX script that is run whenever a SLIP/PPP connection is successfully made.
Whether one's ISP requires the /D, /H, or
/C option will vary according to the ISP's configuration and
whatever mail software is in use on the mailhost. Not all mail softwares
even have a concept of a "channel", for example. If none of the options
is supplied, the default action is to act as if the /H option
had been used.
To attempt to trigger remote delivery of mail queued for the domain
my.domain on the server mailhub.remote.domain:
[c:\]etrn /d my.domain mailhub.remote.domain
/V/E/HELOEHLO/HELO command first.
HELO and EHLO are not required parts of the
ETRN protocol and
good servers will just ignore them if they are sent.
Sending them is in most cases just a waste of a round-trip delay.
/C channel/D domain/H host