Member Avatar for psworx

Dear Guys,

Would anyone know why after sending a single email to around 12,000 people from various distribution lists they would receive that same email in the region of 30 to 130 times additionally.

We've been going round in circles trying to sort this out and are unable to send a mail with the new system incase this happens again (Possible legal action threats have been expressed already as a result of last weeks blunder)


The setup is as follows:

Windows 2003 Server (Service Packed and Patched to date)
Office Outlook 2003 (Same as above)

Behind a router so no firewall is installed, no antivirus is installed either, thus emails arnt scanned on the way out (or being duplicated for that matter) (Yes i know im asking for trouble here however the less variables in the sum the less to go wrong)

We have around 7 distribution lists, the main contains around 12,000 clients the others are around 1,000 max each.

Weve checked on where the mail is coming from and it all resolves back to our hosts mail server which we use for the sending of the mails.

Is it possible for someone to have slipped us a rogue email address that once it receives our mailshot it then resends this out spoofing its origin??? (Note: We Bcc'd all the clients so people shouldnt be able to see who it was meant to go out to)

As far as im aware the hosts mail server is using visnetic mail server however i havent verifiend this just yet.


The following is a snippet of one of the emails headers (some items are blanked out for obvious reasons)

= Censored

This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

(generated from )
mailbox is full
------ This is a copy of the message, including all the headers. ------
Return-path: <>
Received: from [] (helo=)
by with esmtp (Exim 4.34)
id 1FjQXs-0003ki-Hv
for ; Fri, 26 May 2006 01:51:17 +0100
Received: from LBSMAILSERVER ([[/I][EMAIL=""][I]xxxxxxxxxx[/I][/EMAIL][I]])
by (VisNetic.MailServer.v) with ASMTP id KNC37895;
Fri, 26 May 2006 01:26:10 +0100
Return-Receipt-To: "LBS Sales" <>
Reply-To: <>
From: "LBS Sales" <>
To: <>
Subject: Stock 25th May
Date: Sun, 10 Mar 2002 01:14:09 -0000
Organization: Living Business Solutions LTD
Message-ID: <>
MIME-Version: 1.0
Content-Type: multipart/related;
boundary="----=_NextPart_000_17FA_01C1C7D3.257A8D60"
X-Mailer: Microsoft Office Outlook 11
Thread-Index: AcHHg6TzSYzY5GWhTCOIJt2N/v+qAA==
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.2663
Disposition-Notification-To: "LBS Sales" <>

This reply is for a full mailbox so it might not help here however it's worth a shot.


Any help regarding this issue would be great as im tearing out whats left of my hair.

TIA


P Davidson

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  • Latest Post Latest Post by ispit

Dani AI

Generated

— this kind of “one send, many duplicates” usually narrows to a few practical causes: overlapping/expanded distribution lists that duplicate addresses, an MTA/gateway that is re-submitting or splitting batches, or downstream loops/auto-responders that cause re-injection. ’s note about Exchange/POP connectors is relevant if any part of your send path uses a POP gateway or connector that can re-download/resubmit mail.

Quick diagnostic checklist you can run now:

  • Stop any further bulk sends until you have a controlled test.
  • Send the same test message to a small set of addresses you control (different providers). For each duplicate received, compare the Message-ID and the Received: chain in the raw headers. Identical Message-ID across copies = the MTA re-sent the same item; different IDs = multiple independent submissions. The Received: lines show where copies diverged.
  • On the sending host ask for/mailgrep your SMTP logs for that Message-ID and for repeated submissions around that timestamp. Look for multiple queue entries or repeated successful deliveries to the same destination.

Practical fixes and mitigations:

  • Flatten and dedupe every distribution list before sending (export to a CSV or spreadsheet and remove exact duplicates). Nested lists are a common, silent cause.
  • Disable any “request read/delivery receipt” or disposition headers when doing mass mailings; many auto-responders and forwarding systems behave badly when those are present.
  • If the sending server (or your host) is implicated, get its SMTP transaction logs and queue view from your host/support and consider patching/updating the MTA or moving to a dedicated bulk-mail solution for large lists.

If you can post one sanitized raw header from a duplicate plus the Message-ID (and one or two relevant outbound log lines), it’s usually possible to say definitively whether the resends are coming from your side or downstream.

Member Avatar for ispit

I've had the same issue with my Exchange 2003 server. My users send an email with many recipients in the BCC filed, nothing in the To field. Some recipients complained of multiple copies. We tried using both a smart host and using DNS - same problem.

In my previous position I came across the issue from the recipients point of view - their SBS Exchange 2003 needed the POP3 connector patch to fix the problem.

Any ideas?

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