problems and this list

David Ford david at
Tue Jul 10 15:18:18 CEST 2007

Wolfgang S. Rupprecht wrote:
> Marco Barreno <barreno at>
> writes:
>> Can someone with admin access to the list machine send me the SMTP
>> logs for one of the duplicated messages?  I'm working in the Gmail
>> group at Google for the summer and I can have someone try to diagnose
>> the problem from this end.  The full SMTP logs would be helpful.
> I don't have access there, but I can fill in part of the puzzle.  
> At least one of the opemoko machines at opens an smtp
> connection back to the sending domain to verify the sender address of
> any incoming message.  The smtp-back machine has messed up DNS.  The
> claimed rDNS for that IP is "" but the forward DNS check
> for that "" doesn't list as a valid
> address.  If the sending machine is checking for spammers claiming a
> bunk DNS name will reject's SMTP verify.  The opemmoko
> machine will then interpret that failed smtp verify attempt as the
> verified address not existing and will decline the initial incoming
> transfer.
> In short, folks really need to check the forward and backward DNS and
> make sure it is consistent, especially if that machine tries open an
> outgoing SMTP connection (such as the attempted verification).
> Jul  9 12:48:17 arbol postfix/smtp[26802]: 29AF91C98001: to=<xxx at>,[]:25, delay=6.2, delays=0.18/0.04/5.4/0.64, dsn=4.0.0, status=deferred (host[] said: 451 Could not complete sender verify callout (in reply to RCPT TO command))
> Jul  9 12:55:35 arbol postfix/smtpd[26864]: warning: address not listed for hostname
> Jul  9 12:55:35 arbol postfix/smtpd[26864]: connect from unknown[]
> Jul  9 12:55:36 arbol postfix/smtpd[26864]: NOQUEUE: reject: RCPT from unknown[]: 554 5.7.1 Client host rejected: cannot find your hostname, []; from=<> to=<xxx at> proto=SMTP helo=<>
> Jul  9 12:55:36 arbol postfix/smtpd[26864]: disconnect from unknown[]
> Jul  9 12:55:38 arbol postfix/smtp[26863]: 29AF91C98001: to=<xxx at>,[]:25, delay=447, delays=441/0.05/1.2/4.3, dsn=5.0.0, status=bounced (host[] said: 550-Verification failed for <xxx at> 550-Called: 550-Sent:     RCPT TO:<xxx at> 550-Response: 554 5.7.1 Client host rejected: cannot find your hostname, [] 550 Sender verify failed (in reply to RCPT TO command))
> -wolfgang
That wouldn't cause duplicates.

You got a 550 error which means delivery was not attempted.

I'll repeat again because a lot of people are coming up with some kinda
wild answers.

Google mail was causing dupes within google mail -before- it talks to
any server outside of google mail.  I posted the smtp logs of a message
from one dupe chain that revealed this.  I compared it with two other
dupe chains and they both showed the same internal problem.

Regardless it appears to have been fixed as google emails are no longer
making dupe chains.

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