users getting bounce back messages (Full Version)

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berryguru -> users getting bounce back messages (11.Nov.2010 1:09:42 PM)

I'm having a little difficulty troubleshooting a bounce back issue.  Various users are getting bounce back messages as the one shown below.  I don't see them stuck in the queue, and I've verified that we aren't on any Blacklists.  I'm fairly new to Exchange and I'm not exactly sure where else I should look.  It seems that the bounce back message is rather vague, as opposing to other times its given me more info.  I could be wrong, the answer could be staring me right in the face.

I've edited the domain name for security reasons.

From: Mailer Daemon []

The attached message could not be delivered to the recipients listed below.
The original message was rejected at Wed, 10 Nov 2010 16:00:35 +0000
----- The following addresses had permanent fatal errors ----- <>
   rejected by inbound/f6993615-5023-40cb-a1f7-deae592b0dba/ - relay/RELAY

Any thoughts or direction on troubleshooting.  I'd like to learn how to diagnose these kinds of problems.


uemurad -> RE: users getting bounce back messages (11.Nov.2010 7:33:04 PM)

First, understand that a bounce indicates that the message tried to be delivered and failed.  For that reason it's not going to be in any queue unless the NDR indicates it will be retried.

Next, you need to understand what is meant by relaying.

Finally, you need to understand about how Exchange attempts to route messages.  That's the only part of your issue that is directly related to Exchange.  The question I have for you is, are you sending your outbound messages to a smarthost, or are you using DNS to determine where to send them?

berryguru -> RE: users getting bounce back messages (15.Nov.2010 1:16:37 PM)

Per your blog description, we are using DNS to determine where to send the messages.  The descriptions on your blog made it very easy to understand smarthosts and relaying.

uemurad -> RE: users getting bounce back messages (15.Nov.2010 9:33:46 PM)

I'm glad my descriptions were easily understood.  It's easier to point people there than write it out each thread.

Since you are using DNS to route the messages, the next step is to make sure the relaying is not being attempted because of your configuration.

On your Exchange server, use NSLookup and Telnet to verify whether you are sending directly to the recipient system.  Compare that to where your Exchange server sent the message that bounced.

berryguru -> RE: users getting bounce back messages (16.Nov.2010 4:07:12 PM)

I agree.  I've got it bookmarked under my Exchange bookmarks.

I fired up Telnet and attempted to send directly to the recipient, and it failed.  I tried my personal Gmail account and that failed too.

250 Hello []
250 2.1.0 ...Sender OK
rcpt  550 5.7.1 Unable to relay for

The Internet Header of that email from the that bounced back in my inbox

Microsoft Mail Internet Headers Version 2.0
Date: Mon, 15 Nov 2010 23:32:22 -0800
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
X-DSNContext: 7ce717b1 - 1418 - 00000004 - C00402D1
Message-ID: <>
Subject: Delivery Status Notification (Delay)
Content-Type: text/plain; charset=unicode-1-1-utf-7
Content-Type: message/delivery-status
Content-Type: message/rfc822

X-MimeOLE: Produced By Microsoft Exchange V6.5
Content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: multipart/alternative;
Subject: email test
Date: Mon, 15 Nov 2010 11:24:33 -0800
Message-ID: <BB0A9A9361DA714E93EE61CC4F19E33705D985B5@company.local>
Thread-Topic: email test
thread-index: AcuE+rvdGIErLA5MTIyuQv02lqYNsg==
From: "User Name" <>
To: <>

Content-Type: text/plain;
Content-Transfer-Encoding: quoted-printable

Content-Type: text/html;
Content-Transfer-Encoding: quoted-printable


uemurad -> RE: users getting bounce back messages (17.Nov.2010 1:17:04 AM)

I want to be sure you understood the reason for the NSLookup and the Telnet tests.

NSLookup can tell you where the recipient system expects mail to be sent.
Telnet simulates the message delivery process.

When you used Telnet, did you connect to the FQDN or IP address specified by the results of the NSLookup commands?
If so, you may have a DNS issue where the DNS server you are connecting to has incorrect or stale information.

In any case, the Relay failure indicates that you are connecting to a SMTP system that does not accept mail for the TO address you are using.

berryguru -> RE: users getting bounce back messages (6.Dec.2010 7:17:18 PM)

I left this thread dormant for awhile, but I've not forgotten about it.  I found out what the issue was, reverse DNS was not setup!

Once I setup the reverse DNS, I was successful in about 90% of the emails being sent out.

So at this point in time with the reverse DNS setup properly, we are getting the following bounce back message

There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            < #5.5.0 smtp;550-XM-RJCT22: [x.x.x.x] is prohibited from connecting to OtherServer mail>

This is yet another vague error message.

berryguru -> RE: users getting bounce back messages (7.Dec.2010 4:53:56 PM)

Any thoughts???

uemurad -> RE: users getting bounce back messages (19.Dec.2010 3:40:41 AM)

Apologies if you were waiting for me to respond.  I've been away from the forums for a while.

I suggest you look to your SMTP logs for more information about why your messages are not being accepted.  Specifically you are looking for the return codes from the other server.  Let me know if you have any questions about getting or interpreting the information.

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