Hi all,

We have recently migrated from a local provider email hosting plan to  a new in premises exchange 2013 STD SP1 installation and we are having an issue while sending some emails out.

Most of our communication is ok, but on some specific customers we send emails we get NDR with a "mailbox unavailable result", which can't be right because we used to (and we are still able to)receive emails from them.

Any Ideas on what we need to do to solve the issue.

We have currently disabled TLS on our send connector to check whether this solves the issue with no success.

more details on our installation is we are using a single server for our exchange 2013 (mailbox & Client access roles), installed on a Windows 2012 Server, and are using a mixture of Outlook 2007, 2010 and 2013 as Clients. The problem has nothing to do with the clients as we get the same NDR's from all version of outlook

Hello there, 

Did you create new connectors or modify the default? The default connector is all that you need to change, just enable Anonymous and then restart Transport. 

https://technet.microsoft.com/en-us/library/bb232021(v=exchg.141).aspx

Keep us posted 

Hi,

This can be the nickname cache. Test this by clearing for a single email address first. You may refer the following kb article: https://support.microsoft.com/en-us/kb/287623

Hi. We have modified the default connector by enabling anonymous users as mentioned. Again I mention we have a problem on some email accounts, where we know they exist but we get NDR's with "mailbox unavailable". Please also note that when we try to send to the email addresses that make us the issues from a gmail or hormail the email goes ok. 

Thank for your reply. Unfortunately this is not the issue either because the email profiles on the computers are new, and the problem is from all the clients were we double confirm the email address we send to, both from the client and exchange server.  The problem we are having seems to be something like our exchange server is able to reach the foreign mail server, but is unable to locate the mailbox we are trying to send to, although we are sure the mailbox exists. 

Can you share the exact NDR generated?

Requested rejected your message to the following email addresses: <customer email>@Proludic.co.uk (<customer email>@Proludic.co.uk)
Requested gave this error:
Requested action not taken: mailbox unavailable 
A problem occurred while delivering this message to this email address. Try sending this message again. If the problem continues, please contact your helpdesk.
 





Diagnostic information for administrators: Generating server: SRV-EXCH.blueice.local
<customer email>@Proludic.co.uk
Requested
Remote Server returned '550 Requested action not taken: mailbox unavailable'
Original message headers:

Received: from SRV-EXCH.blueice.local (10.10.1.3) by SRV-EXCH.blueice.local
 (10.10.1.3) with Microsoft SMTP Server (TLS) id 15.0.847.32; Fri, 3 Jul 2015
 20:22:53 +0300
Received: from SRV-EXCH.blueice.local ([fe80::2892:6ee2:6cf8:9875]) by
 SRV-EXCH.blueice.local ([fe80::2892:6ee2:6cf8:9875%12]) with mapi id
 15.00.0847.040; Fri, 3 Jul 2015 20:22:53 +0300
From: Administrator <Administrator@blueice.com.cy>
To: "<customer email>@Proludic.co.uk" <<customer email>@Proludic.co.uk>
Subject: test email 
Thread-Topic: test email 
Thread-Index: AQHQtbTUsgbJYIvwU0+/yq/oejuC5A==
Date: Fri, 3 Jul 2015 17:22:53 +0000
Message-ID: <fb46e3a59d884293aad8e3bd1734f03f@SRV-EXCH.blueice.local>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [213.149.183.117]
Content-Type: multipart/alternative;
   boundary="_000_fb46e3a59d884293aad8e3bd1734f03fSRVEXCHblueicelocal_"
MIME-Version: 1.0

Hello,

Thanks for providing the details. The error message shows an issue at the sending domain (Proludic.co.uk). I guess they use mailenable email service as the error ('550 Requested action not taken: mailbox unavailable') is a mailenable email service specific error code. So contact their administrator and tell them the specific error and pass the whole NDR. They wanted to re-enable the email reception feature at their end

Hi,

Does the issuehappens in Outlook only or also in OWA?

If you still have not tried with OWA , please test it and tell us the result.

Please ensure that you have the correct DNS record(MX record,A record) for the Exchange Server.You can use Nslookup to check it.

Please refer to the below link :

http://support.microsoft.com/kb/200525

Then try to restart Microsoft Exchange transport service.

If it doesn't work, please refer to Manu's suggestion to contact with their domain administrator.

Regards,

David

• Edited by David Wang_Microsoft contingent staff 4 hours 14 minutes ago

Hi,

Does the issuehappens in Outlook only or also in OWA?

If you still have not tried with OWA , please test it and tell us the result.

Please ensure that you have the correct DNS record(MX record,A record) for the Exchange Server.You can use Nslookup to check it.

Please refer to the below link :

http://support.microsoft.com/kb/200525

Then try to restart Microsoft Exchange transport service.

If it doesn't work, please refer to Manu's suggestion to contact with their domain administrator.

Regards,

David

• Edited by David Wang_Microsoft contingent staff Monday, July 06, 2015 3:14 AM

Hi David, 

Yes the problem occurs in OWA as well. I managed to find out the following today :

When I switch my send connector to route email trough a SMART HOST, then the emails deliver ok. The Problem occurs when we "route email through MX record associated with recipient domain".  The problem is that I cannot leave the SMART HOST server as a default, because it belongs to our provides, which everyone uses and it's usually blacklisted very often. 

Additionally in reply to Manu's post, I have contacted the other party, and they told me that there is nothing they can do, since those guys have a lot of customers with exchange and they receive emails from everyone else just fine..... 

In a bit of dead end really ..... Please Help !!!!

Hi,

Try to run the below command to adjust the connector setting:

Set-Sendconnector -identity <sendconnectorname> -IgnoreSTARTTLS $true

Regards,

David

Hi David and thanks for your reply. 

We have disabled TLS (also mentioned in original post)..... any other ideas ???? Is there any possibility that this is a bug of the send connector of Exchange 2013 SP1 ?