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04.10.2006 at 10:17AM PDT, ID: 21808500
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8.8

Disabling NDR's on Exchange server

Asked by rid in Email Clients

Tags: , ,

HI all.

I had a discussion with our IT consultants and it makes me want to ask a few questions:

1. If you send a message to baduser@domain.org and baduser doesn't exist, the domain.org mailserver can cut off the SMTP dialogue by saying: "550: user unknown" (or similar) and that is an end of the conversation.
Is this correct?

2. Assuming the above is correct, you can expect a failure report from YOUR mail server, as it concludes there is no recipient with the baduser address, IF your mail server is built to do this. This message is not generated externally.
Is this correct?

3. Exchange mail servers seem to go about this in another manner. They (seem to ) accept incoming mail even if the address is bad and then they create an NDR which is dispatched to the return address of the original message.
Is this correct?

The discussion appeared as I (being "postmaster" of our domain) got a number of NDR's in return from servers that also sent NDR's for bad addresses.... The original message was of course an incoming SPAM message with a spoofed sender, one that had a valid domain name but a bad username... I proposed to switch off NDR's, but our consultants balked at that. I see no real value in NDR's, why don't they like the thoght of switching them off?

Hope the questions are clear enough (looks a bit tangled now, but anyhow).
/RIDStart Free Trial
 
Keywords: Disabling NDR's on Exchange server
Title
1 NDR Attacks
2 Spam bring returned as NDR's
3 NDR
4 Possible NDR attack - advice needed
5 After exchange NDR Attack
6 Spam mail as NDRs(Non Delivery Rep…
 
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[+][-]04.12.2006 at 02:24AM PDT, ID: 16434418

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[+][-]04.12.2006 at 03:31AM PDT, ID: 16434690

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[+][-]04.12.2006 at 04:00AM PDT, ID: 16434802

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About this solution

Zone: Email Clients
Tags: exchange, ndr, 550
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Solution Provided By: upul007
Participating Experts: 1
Solution Grade: A
 
 
[+][-]05.06.2006 at 12:54PM PDT, ID: 16622699

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[+][-]05.06.2006 at 10:48PM PDT, ID: 16623892

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