Notification of non existant email user

rockethobbit
rockethobbit used Ask the Experts™
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Exchange 2003

Is there a feature of exchange that will notify a system administrator/user of incoming mail that is for exchange users who no longer exist?
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Commented:
Exchange Server MVP Michael B Smith has written a script that does exactly this:
http://theessentialexchange.com/blogs/michael/archive/2007/11/13/exchange-200x-catchall-script-version-2.aspx

Note within the discussion that he mentions the Turbo Geeks tool MailBasket which performs the same function.  This isn't free but does have a 30-day free trial.
http://www.turbogeeks.com/products/mailbasket.asp

Author

Commented:
Does anyone else out there know of a BUILT-IN solution that takes care of this?

Commented:
Well, BUILT-IN solution is that you go to the properties pages of your SMTP virtual server
Exchange System Manager > Orgname > Servers > Servername > Protocols > SMTP > vsname > right-click, properties
Then Messages tab, then Send copy of non-delivery report to: and enter an SMTP address.

This doesn't get the actual mail forwarded, but it at least lets you know what addresses they are being sent to.  You can then add any address here to a mailbox, or my favorite is to add them to a distribution list with no members, causing them to be distributed into a black hole 12 light-years just the other side of the Andromeda Galaxy.
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Alan HardistyCo-Owner
Top Expert 2011

Commented:
When you say 'A user who no longer exists' - I am assuming that you mean that their account and Exchange mailbox has been deleted?
If this is the case - there is no Built-In way to do this unless you retain the email address / account and auto-forward the emails to an existing user and have them setup a rule that moves the emails based on the Sent To field to another folder.  They can they reply to this.
Other than that - it's a big NO.

Author

Commented:
Clarification. I think I am barking up the wrong tree.

What I think I need is NDR turned back on. Users are sending this organization emails, but they are not getting NDR's back saying that the message was not delivered due to the recipient not existing.

This feature was turned off for spam reasons, but they would like it turned back on. I think I know where it is located, but could someone please confirm?

Thanks.
Alan HardistyCo-Owner
Top Expert 2011
Commented:
Open up Exchange System Manager, Expand Global Settings, Select Internet Message Formats.  In the right-hand pane, right-click on Default and select Properties.
On the advanced Tab - select Allow Non Delivery Reports.

Commented:
Here's the KB article:
http://support.microsoft.com/kb/294757

Global settings > Internet Message formats, select default, properties, advanced, make sure "allow NDRs" is checked.
Expert of the Quarter 2009
Expert of the Year 2009
Commented:
This is a really bad idea.
It means that your server accepts all email for non-existent users, in order to generate the NDR.
That puts your server at risk of an NDR attack or a directory harvest attack, with the mailbox of whoever is getting the messages will receive a copy of all of the messages.

The most efficient way of dealing with emails to non-existent users is to use recipient filtering, so that you drop the emails at the point of delivery. I have a client who drops 10,000 messages a day to non-existent users, and they only have 30 staff.

Simon.

Commented:
The thing to keep in mind with dropping all NDRs, though, is that if you have someone with an easily-misspelled name (mine, for example, or Michelle O'Neal for another), and you don't think up all of the permutations, then people will send them emails to misspellings (michel.oneill, michele.oneall, etc) and they will silently drop.  At that point there is a risk of important customers believing that your users are ignoring them.

But yeah, in the age of Joe Jobs with their backscatter, and dictionary harvesting, we get more things that must be scrawled on our whiteboards.

-tom

Author

Commented:
I believe that is currently enabled, but that does not generate the NDR does it? The customer is concerned that their customers are sending emails to non existent users assuming they receive the email and then nothing happens in regards to the email sent.
Alan HardistyCo-Owner
Top Expert 2011

Commented:
Drop me a email (via my profile) and I'll test out some random usernames and let you know what response (if any) I get.
Expert of the Quarter 2009
Expert of the Year 2009

Commented:
If you have recipient filtering enabled then the REMOTE server generates the NDR and it is returned to the user immediately. If you do not have recipient filtering enabled then your server accepts the message, then attempts to NDR it back, which may not always reach the sender.
It is not possible when Exchange is the originating server (sender) for the sender to not receive the NDR, because it is generated on the Exchange server. I cannot comment about other mail servers.

You can test what happens yourself by either sending to a known non-existent address from an external account or by using telnet.

Simon.

Author

Commented:
I am meeting with the customer next Tuesday so I am leaving this open until then.

Author

Commented:
We decided to leave allow NDR's OFF to prevent problems with spam. Recipient filtering is enabled so sendings users email system should send their users NDR's. We will turn on out of office message for users who have left company to auto-send warning this account not active. Leave account up for 1hr then delete.

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