Re: duplicate emails when using: Deliver messages to both forwarding address and mailbox

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I worked with Microsoft tech support on this today and was able to fix
ours. Hope this works for you too:

Short answer: Enable Integrated Windows Authentication on the SMTP
Virtual Server on both front-end and back-end servers. See
http://support.microsoft.com/kb/843106/

Here's what the Microsoft tech led me through.

1. Enable Diagnostics at Maximum level in order to generate data for
diagnosing the problem. We did this by going to the Exchange System
Manager - Administrative Groups - <Domain> - <Server>. Go to Properties
of the server. Click on Diagnostics Logging. Scroll to
MSExchangeTransport. Enable Maximum logging on all categories under
MSExchangeTransport.

2. Now send a test email to recreate the condition. (Sent a message to
myself from gmail. I had my account set up to forward to a Yahoo
address.)

3. Now look in the Event Viewer - Application. AHA! Oodles of error
messages that were not there before have now appeared, as the diags is
logging detailed messages from SMTP. The errors are all the same:

Source: MSExchangeTransport, Category: SMTP Protocol, Event ID:7010.
The message: "This is an SMTP protocol log for virtual server ID 1...
The client at <IP address of Front-End Exchange server> sent a
"xexch50" command, and the SMTP server responded with "504 Need to
authenticate first".

4. A quick search online Found KB 843106 - "How to troubleshoot the
"504 need to authenticate first" SMTP protocol error". In here, we
learn that if you disable Integrated Windows Authentication on the SMTP
Virtual Server, then "Messages to alternate recipients may cause
duplicates."

5. Bingo! Enabled Integrated Windows Authentication for the SMTP
Virtual Server on both the front end and back end Exchange servers:

a. In Exchange System Manager, expand Administrative Groups, expand
Servers, expand Exchange Server Name, expand Protocols, and then expand
SMTP.
b. Right-click the SMTP virtual server. (By default, this is named
Default SMTP Virtual Server.)
c. Click Properties, click the Access tab, and then click
Authentication. Make sure that the Integrated Windows Authentication
check box is selected

Happy ending. It's fixed.

How did it start?

About a month ago, my manager and I reviewed the SMTP settings on the
server. With the intent to lock down the server, we made some changes,
one of which was disabling the option to use Integrated Windows
Authentication. (We did not want users setting up SMTP accounts on
their workstations and sending SMTP email.)

Several days later, some users reported the duplication of forwarded
emails, but we did not connect the two.

It seems that our front-end server was having an issue authenticating
to the back-end server. Exactly why this resulted in duplicate emails
is a bit of a mystery to me still.

.

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