Mailing List CGatePro@mail.stalker.com Message #99155
From: Urban Loesch <bind@enas.net>
Subject: Re: EHLO vs HELO
Date: Fri, 08 Jan 2010 19:22:49 +0100
To: CommuniGate Pro Discussions <CGatePro@mail.stalker.com>
Hi,

I'm not sure what CGP will do if EHLO fails. Perhaps the guys from Communigate would know.

From the manual (Server Version 5.0.X):

...
Always use EHLO
    If this option is selected, the SMTP module always sends the EHLO command to remote servers, trying to establish the extended SMTP (ESMTP) protocol.
    If this option is not selected, the SMTP module checks the remote server greeting line. The SMTP module sends the EHLO command only if this line contains the ESMTP word.
...

This means: if the greeting line from the destination server contains the word "ESMTP", CGP sends the EHLO command. If not it sends the HELO.

According to the RFC (I don't remeber which one) the server greeting line should contain its own hostname and some other stuff like the ESMTP word.

Example:

1) Server supports EHLO:
220 $ITS_OWN_HOSTNAME ESMTP Welcome to my Mailserver!
quit
221 2.0.0 Bye

2) Server doesn't support EHLO (no ESMTP word in the greeting line):
220 $ITS_OWN_HOSTNAME Welcome to my Mailserver!
quit
221 2.0.0 Bye

Regards
Urban



Jeff Wark wrote:
I was under the impression if EHLO resulted in an error, the client [server sending the email in this case] would have to fall back to HELO and the transaction would happen normally.

I guess that impression was wrong it was good I didn't casually "Always use 'EHLO'".


Urban Loesch wrote, at 1/8/2010 12:26 PM:
Hi,

I think there are still many "old" mailservers which don't understand
"EHLO". We have had a few problmes in the last 2 years, but not many. I
recommend to not forcing always "EHLO".

Regards
Urban


Jeff Wark wrote:
Has anyone ever experienced problems with forcing your server to
"Always try 'EHLO'"? We're looking at it and want to know of any
negative experiences.


#############################################################
This message is sent to you because you are subscribed to
the mailing list <CGatePro@mail.stalker.com>.
To unsubscribe, E-mail to: <CGatePro-off@mail.stalker.com>
To switch to the DIGEST mode, E-mail to <CGatePro-digest@mail.stalker.com>
To switch to the INDEX mode, E-mail to <CGatePro-index@mail.stalker.com>
Send administrative queries to <CGatePro-request@mail.stalker.com>

Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster