We're looking to set up an e-mail sub-domain for a project, and we need to set up a catch-all e-mail address, so whether people send project updates to project1234, or project4321, it will redirect to the one existing e-mail account.

  • I've set up the sub-domain MX in our public DNS.
  • I've set up the sub-domain in EMC, per this article. We do not have an edge transport server, but the same settings are under Hub Transport, which I thought would be the same.
  • I've set up the catch all e-mail address per this article.

The sub-domain works when I send directly to the one existing account with an e-mail address in the sub-domain, and it works if I set up specific aliases on the account, but it's not working as a catch all. When I test from my Gmail to a non-existent address on the sub-domain, it is rejected as an unrecognized recipient.

At first I considered that it might be our spam filter (McAfee hosted) blocking these messages. But when I added an alias in Exchange and did not set up the user in McAfee, it still came through, so it really appears to be something misconfigured or missing in Exchange.

I set up the Transport rule to be "when a recipient's address matches '@sub.example.com$' copy the message to 'existingAccount@sub.example.com'"

I've also tried "when a recipient's address contains specific words 'sub.example.com'" and any other variation I could think of to get a generic catch all for the sub-domain... nothing has worked so far, except creating an alias (which would defeat the purpose of having a catch all).

Does anyone have experience with setting one of these up, and so could provide direction on what I'm missing?

P.S. the NDR

Diagnostic information for administrators:

Generating server: example.com

 #550 5.1.1 RESOLVER.ADR.RecipNotFound; not found ##

Original message headers:
Received: from p01c12m115.mxlogic.net ( by
 server.local.example.com ( with Microsoft SMTP Server
 (TLS) id 14.0.722.0; Tue, 9 Aug 2011 11:54:09 -0400

Received: from unknown [] (EHLO mail-wy0-f170.google.com)  by
 p01c12m115.mxlogic.net(mxl_mta-6.10.0-2) over TLS secured channel  with ESMTP
 id f18514e4.0.181220.00-2292.264602.p01c12m115.mxlogic.net (envelope-from
 <me@gmail.com>);   Tue, 09 Aug 2011 09:54:08 -0600 (MDT)

Received: by wyf23 with SMTP id 23so97339wyf.29        for
 <new@sub.example.com>; Tue, 09 Aug 2011 08:54:06 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=gamma;
MIME-Version: 1.0

Received: by with SMTP id i8mr1726607wed.61.1312905246774; Tue, 09
 Aug 2011 08:54:06 -0700 (PDT)

Received: by with HTTP; Tue, 9 Aug 2011 08:54:06 -0700 (PDT)
Date: Tue, 9 Aug 2011 11:54:06 -0400
Message-ID: <CAE=Hmibpw4TVZ5MnG81qBjrUdPRc93eNhx8ACD71u4rjKo7evw@mail.gmail.com>
Subject: test test test
From: Me <me@gmail.com>
To: <new@sub.example.com>
Content-Type: multipart/alternative; boundary="000e0ce0cf08db956b04aa149235"
X-Spam: [F=0.2000000000; B=0.500(0); spf=0.500; STSI=0.500(0); STSM=0.500(0); CM=0.500; MH=0.500(2011080922); S=0.200(2010122901); SC=none]
X-MAIL-FROM: <me@gmail.com>
X-AnalysisOut: [v=1.0 c=1 a=nDghuxUhq_wA:10 a=BLceEmwcHowA:10 a=nS36O97Bj3]
X-AnalysisOut: [wUElCrIrAA:9 a=wPNLvfGTeEIA:10]
Return-Path: me@gmail.com

Received-SPF: Neutral (server.local.example.com: is
 neither permitted nor denied by domain of me@gmail.com)

Final-Recipient: rfc822;new@sub.example.com
Action: failed
Status: 5.1.1
Diagnostic-Code: smtp;550 5.1.1 RESOLVER.ADR.RecipNotFound; not found

Per that article, having a Hub Transport do the job won't work:

Recipients are resolved before messages pass through the Transport Rules agent on Hub Transport servers. Therefore, transport rules on Hub Transport servers can't be used to copy or redirect messages to a catch-all mailbox.

  • wow, thanks :P I'm sure I read that, but I must have mentally skipped over it in the process of trying to set it up. – White Island Aug 9 '11 at 16:50
  • You actually can do this. See my answer. – Massimo Dec 11 '13 at 12:52

You can create a catch-all mailbox by using a transport rule which redirects all messages addressed to unknown users to the catch-all mailbox.

However, in order for this to work, you will need to configure the SMTP domain as an "internal relay domain", as opposed to an authoritative domain; otherwise, Exchange will reject all messages addresses to non-existent users before even starting to process the transport rules.

  • Thanks this helped me as I ran into the same issue as the OP. – Chance Mar 23 '15 at 20:47

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