Error in SMTP sequence - ReadList.com

11 msg	SMTP authentication with saslauthd against PAM

Error in SMTP sequence
\ Rob Sterenborg (13 Apr 2007)
. \ (Wietse Venema) (13 Apr 2007)
. \ (Wietse Venema) (13 Apr 2007)
. . \ (Wietse Venema) (13 Apr 2007)
. . . \ Rob Sterenborg (13 Apr 2007)
. \ Rob Sterenborg (18 Apr 2007)
. . \ (Wietse Venema) (18 Apr 2007)

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Subject:	Error in SMTP sequence
Group:	Postfix-users
From:	Rob Sterenborg
Date:	13 Apr 2007

Hi all,

We are running Debian 4 with Postfix-2.3.8-2+b1.
Sometimes when a MTA connects with us and tries to send an email, I get
emails like this in the postmaster mailbox:

=================
Transcript of session follows.

Out: 220 mx3.netsourcing.nl ESMTP Postfix
In: EHLO mail.pleyade.nl
Out: 250-oehoe.dcyb.net
Out: 250-PIPELINING
Out: 250-SIZE 15360000
Out: 250-VRFY
Out: 250-ETRN
Out: 250-ENHANCEDSTATUSCODES
Out: 250-8BITMIME
Out: 250 DSN
In: MAIL FROM:<xxxx>
Out: 250 2.1.0 Ok
In: xxxx
Out: 502 5.5.2 Error: command not recognized

Session aborted, reason: lost connection
=================

Clearly, what went wrong is that the MTA failed to send "RCPT TO: " in
front of the recipient email address. (I sniffed the line and it's
actually sent like this so it's not a problem on our side.) It doesn't
always happen: most email from these domains (97-99% or so) is delivered
normally.

So far, the only thing these MTA's seem to have in common is that they
are Novell GroupWise servers:

=================
$ telnet mail.pleyade.nl 25
Trying 212.104.204.78...
Connected to mail.pleyade.nl.
Escape character is '^]'.
220 mail.pleyade.nl GroupWise Internet Agent 6.5.4 Copyright (c)
1993-2005 Novell, Inc. All rights reserved. Ready

$ telnet mail.meavitawoonzorg.nl 25
Trying 193.173.57.179...
Connected to mail.meavitawoonzorg.nl.
Escape character is '^]'.
220 mail.meavitawoonzorg.nl GroupWise Internet Agent 6.5.3 Copyright
(c) 1993-2004 Novell, Inc. All rights reserved. Ready
=================

I could not find anything (useful) about this behaviour Searching for
the words "missing", "rcpt to", "groupwise" and the like did not return
something that describes what happens here.
So, has anyone seen this before and if yes; is this a known problem with
GroupWise and is there a fix or something?

Thanks,
Rob