Im getting the delivery failed from the post master reply. i don't want it. because then poeple can find out all my real users on the exchange. also, i have a lot of users (10K) in my application - and i don't want to create a mailbox for each user.

is it possible to get this done in ex2010 sp1. hub-transport configuration? or i must use edge-transport as indicated in http://technet.microsoft.com/en-us/library/bb691132(EXCHG.80).aspx

  • i have tried to follow this instructions technet.microsoft.com/en-us/library/bb691132.aspx - but it doesnt apply for mailboxes that doesnt exists. – Itay Levin Dec 20 '10 at 18:46
  • i have a lot of users (10K) in my application - and i don't want to create a mailbox for each user. Do you mean you have a web-app which is sending out emails or what ? Please clarify as normally people would have MailBoxes, Mailcontacts in Exchange. – rihatum Dec 21 '10 at 12:48
  • I'm developing a paging application that i want to add to her the ability to send page massages via EMAIL for instance if i have a Pager Number called "itay" i want to be able to send an email to itay@mydomain.com (which doesn't exists) - and i want the catch all redirect the messages to the mailbox pager@mydomain.com (which does exists) - which is the catch all mailbox - and i'm going to use the Exchange webservices managed api in order to get push notification on the emails that were redirected to the pager@mydomain.com (which keep the original from and too of the email message) and than i – Itay Levin Dec 21 '10 at 13:05
  • and than i will send the page to the pager "itay" with the content of the email message. – Itay Levin Dec 21 '10 at 13:05

The NDRs generated by non-existent email addresses are very important. How else would a sender know they have made a mistake and addressed an email incorrectly?

Here is an article about why NOT to use catch all addresses: http://www.allspammedup.com/2010/05/why-you-should-not-use-a-catch-all-email-address/

If you're worried about directory harvesting attacks (where attackers send lots of email to your network and use the NDRs to determine valid and invalid addresses) then you can combat that with any email security product that includes directory harvesting protection.

GFI products do this.

Or you can do it with Exchange 2010's inbuilt security features, by configuring the tarpit interval. Read this article (scroll down to the part about tarpitting):


You can read more about directory harvesting here too (refers to Exchange 2007 but applies to Exchange 2010 as well): http://www.allspammedup.com/2008/12/protecting-exchange-server-2007-from-directory-harvesting-attacks/

  • but you haven't answered my question - why is that not working? From where the NDR is being sent - if i turned off the reecipient filter in the exchange. – Itay Levin Dec 21 '10 at 9:23
  • My real reason for wanting to disable the NDR and create this catch all - is that i want to be able to get all this emails for this mailboxes and handle them myself - i have alot of users in my application and i don't want to create a mailbox for each user. because i'm afraid the exchange might be slow. – Itay Levin Dec 21 '10 at 11:53
  • This answer is misleading, but I can't vote it down (yet).Catch-all mailboxes have lots of legitimate uses and NDRs are not relevant in many of these. For example, a helpdesk ticket system which replies to a user help request with a reply-to address that maps to the original ticket, e.g. "ticket12345@example.org" – Quango Jun 17 '11 at 10:05

It is possible to do, but you need the "CatchAllAgent" from CodePlex.

See this similar question and response:

How can I configure a "catchall account"?

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