Black Holes - not just a space thing!

As users leave your company, you will more than likely delete their mailbox after a certain amount of time. It is then common for the SMTP address of the departed employee to be added to another mailbox, or a public folder, perhaps being monitored by the departed employee's manager. The aim is to make sure that any important business email is acknowledged for some amount of time after the user has left.

Clearly there is a long term issue with this method, since eventually, the monitoring of the messages sent to that address will stop. Removing the SMTP address from the organisation will obviously not stop messages being sent to that address; there are always going to be those pesky spam messages, and additionally, your Exchange server has to generate a non-delivery report for each message.

One solution to put the issue out of your mind is to implement what is sometimes referred to as the 'black hole' method. This allows your Exchange server to simply delete the messages sent to specific SMTP addresses, whilst at the same time never generating a non-delivery report for these messages.

Here are the 3 simple steps to implement the black hole method:

1. Create a distribution list (Exchange 5.5) or a mail-enabled distribution group (Exchange 2000).

2. Make sure that there are NO members in this distribution list/group. This is the key part to this tip.

3. Add the SMTP addresses of the ex-employees to the distribution list/group. Add them as secondary SMTP addresses in exactly the same way you would for a mailbox.

Now, when messages are sent to these problematic SMTP addresses, Exchange silently deletes them. No non-delivery reports are generated, and the administrator no longer has to be concerned about these messages.

Try it. It works well!

Neil Hobson

Chris Meirick on July 27, 2003 at 08:15 AM in How-Tos
« Who's using it?... | Main | Is Your RUS Not Working? »


It doesn't seem to work for me. I made a Domain Local Distribution Group with the email address of I have added several addresses to the group. Under Exchange Advanced, I have checked the box to hide the group from Exchange address lists, and I have selected Do not send delivery reports. I then sent a test email to one of the secondary email addresses and still received an NDR. What gives? Should have I of made a Global group instead of a Domain Local?

Posted by: Roy Avery at Apr 14, 2004 8:12:43 AM

What do you mean by 'I have added several addresses to the group'? Have you added the addresses to the the E-Mail Addresses tab of the group, or have you added actual members to the group?

Posted by: Neil Hobson at Apr 15, 2004 2:16:29 AM

My questions is this: When somone sends a meeting request from a general mailbox, when the recipients respond they get a NDR with an ex associates mailbox that we have already deleted. I tried this Black Hole list and that did not work for my issue. Is there any way to search for deleted mailboxes and remove any reference to them in Exchange 5.5 SP4?


Posted by: Adam at May 6, 2004 6:48:32 AM

Let me correct my first comment and say that I am not having the problems I was complaining of. I was impatient and didn't wait long enough before testing.

Posted by: Roy Avery at May 11, 2004 8:42:00 AM

Dear Neil,
Is there any way we can disable the delivery reports and read reports. Infect if you look at the complex network where I have to monitor 500 mail boxes and around 400 user enable message tracking and they are receiving delivery report as well as read reports in the local domain and delivery report from the outside domain. Ndr concept was not clear to me though on my network this is the biggest problem I am facing. is there any way I can disable delivery and read reports on exchange 2000 server? Thanks in advance...

Kind Regards,


Posted by: Jeet at May 15, 2004 3:11:58 AM

I add global distribution list in ms exchange 2000 (managed by xy user add)xy user to
add user in this group using ms outlook how he do ?

Posted by: venkat at Jun 3, 2004 9:54:19 AM

I have a user that is recieving NDR's from the admin box. I don't know why he is getting them. There are several of us listed as administrators but only one that recieves these messages. We are currently running Exchange 5.5 service pack 4. Can you help me?


Posted by: Melissa at Jun 15, 2004 12:08:22 PM

"Now, when messages are sent to these problematic SMTP addresses, Exchange silently deletes them. No non-delivery reports are generated, and the administrator no longer has to be concerned about these messages."

---This is incorrect as it is sent to the BadMail folder by Exchange and you have to run a scheduled script to delete these files.

Posted by: ozyaus at Aug 29, 2004 11:20:42 PM

Ozyaus, can you elaborate on the BadMail folder, and what steps should be taken specifically? MS's KB doesn't have much to say about Bad Mail. Perhaps even saying where it is? I can't seem to find it... thanks!

Posted by: Colin at Oct 15, 2004 1:51:40 PM

By default it is at C:\Program Files\Exchsrvr/Mailroot/vsi 1/Badmail

This causes the file system to fill up if there are unusually large amount of badmails. I had to relocate this directory elsewhere using this link

There are automated scripts that can be run daily to flush this directory.
!!!Hey I discovered it is all here at

Posted by: ozyaus at Oct 18, 2004 5:03:16 PM

Is there any reason why, after exchange is setup and u look at at properties for a user, all tabs for exchange are there except the exchange advanced tab?

Posted by: rob at Feb 14, 2005 3:50:18 AM

I cannot explore to badmail folder. When I get to vs 1 folder- system goes into hours of work and I do not know command line to delete the badmail folder. My server wants
8.3 file format in command line.

ie.. c:\progra~1\exchsvr\mailroot\vsi 1 (this is where doesnt get to- how
do I enter vsi space 1 in 8.3 format????

Posted by: Cindi at Nov 4, 2005 4:54:38 PM

The command prompt should read as follows: del "c:\program files\exchsvr\mailroot\vsi 1\badmail\*.*" /Q

If your system is configured not to handle "program files" then substitute progra~1 for that portion and the rest should be good.

Posted by: Joel at Nov 28, 2005 9:01:47 AM

After encountering this issue, I did a search and came here. I thought I would recommend a program to help out with deleting files. I hope I am not out of line for mean well.

Here is a great utility where you can add custom directories to delete.

If there are any other safe dir to delete in exchange, I would like to know.

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