also sprach Rino Mardo (on Wed, 12 Sep 2001 07:30:57AM +0800):
> i see it is like using "proto POP3" replacing POP3 with the keyword
> ETRN. ok.
well, try to understand what ETRN does. POP3 means you log into a POP3
server, give it the clear-text password, and then RETR your mail
(that's the command), one after the other.
ETRN means that your MX is configured to transport all mail directly
to your system, and if that is down, then to keep it in a queue (up to
5 days or so, depending on MTA). once your server is online again,
ETRN tells the MX to spool the queue and send everything now - you
don't have to wait for the next retry of the SMTP server, at which
point you may well be down again.
> > do you know your way well with the ideas underlying POP3, IMAP, and
> > SMTP, and do you know the differences between MTA, MDA, and MUA?
> >
> mta, mda, mua yes. but the ideas underlying pop3, imap, and smtp i'm
> still trying to get a grasp of. that's why i asked in a separate thread
> how to get the rfc's of each via email since i only i have email access.
RFC here and there, these are almost overkill if you ask me. a rather
simple way to find out is to sniff the wire with ethereal and see
what's going on in a POP3 or SMTP conversation. it's pretty simple
actually. forget about IMAP for now...
here are some typical examples:
sending an email from fishbowl, my laptop, to embryo, my gateway.
i am speaking ESMTP here... that's extended SMTP
220 embryo.home.madduck.net ESMTP "welcome to the machine..."
EHLO fishbowl.home.madduck.net
250-embryo.home.madduck.net
250-PIPELINING
250-SIZE 10240000
250-ETRN
250 8BITMIME
MAIL FROM: <madduck@madduck.net>
250 Ok
RCPT TO: <rmardo@yahoo.com>
250 Ok
DATA
354 End data with <CR><LF>.<CR><LF>
From: <madduck@madduck.net>
To: <rmardo@yahoo.com>
Subject: testmail
ignore this for now, it's an example email in response to your mail.
martin
.
250 Ok: queued as 8A4261174A
QUIT
221 Bye
SMTP is the basic version, although most MTA's speak ESMTP. you can
always see that in the 220 greeting of the server. ESMTP has direct
mappings to SMTP commands:
SMTP <=> ESMTP
HELO EHLO
MAIL MAIL
RCPT RCPT
DATA DATA
TURN ETRN
there are more, you need to know just these though for normal ops.
an ETRN session is as follows:
220 embryo.home.madduck.net ESMTP "welcome to the machine..."
EHLO fishbowl.home.madduck.net
250-embryo.home.madduck.net
250-PIPELINING
250-SIZE 10240000
250-ETRN
250 8BITMIME
ETRN fishbowl.home.madduck.net
250 Queuing started
QUIT
221 Bye
a POP3 session looks like this:
+OK Solid POP3 server ready
USER madduck
+OK username accepted
PASS mypassword
+OK authentication successful
STAT
+OK 1 1126
RETR 1
<email with all headers here>
.
DELE 1
+OK message 1 marked as deleted
QUIT
+OK session ended
in both POP3 and SMTP, there is a RSET command, which will reset the
connection to the original state.
your best bet: install postfix and courier-pop3 from woody, and then
go and play with it. you'll best go with netcat (the `nc` command),
connection to ports 25 and 110.
and if you have questions, i'll gladly answer them.
martin; (greetings from the heart of the sun.)
\____ echo mailto: !#^."<*>"|tr "<*> mailto:"; net@madduck
--
i wish this wish not to be granted!
-- achilles (hofstadter's geb)
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