Question : 5.7.1 Unable to relay; Mailbox Unavailable; new domains; Exchange 2003

Hello Experts!

I have two Exchange 2003 Servers hosting mailboxes for about 40 domains.  I recently tried to add another domain and began having delivery problems.  After much troubleshooting I stepped back and setup a TEST account and domain (a completely different domain from the one we started) and noticed that the issues continued.    I rather not bore you guys with details and jump right to my last step that had left me scratching my head:

- If I OPEN Relay on both exchange servers, all mail delivery for new domains is successful.  If I CLOSE Relays on both exchange servers (as we want and have had for the past 5 years) delivery to the NEW domains fails with the errors below.

- I used http://www.testexchangeconnectivity. com to generate the error in the Code Snippet. I also have my NDR below to show you the issue.

- The problem occurs when mail is sent from any server EXCEPT internal (internal mail flows through fine).  

- Recipient Policies (obviously I hope) have the new domains in them and the changes propagate out.

- The last time we added a domain was about 3 months ago, and had no issues.  


Delivery to the following recipient failed permanently:

    [email protected]m

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 5.7.1 Unable to relay for [email protected]m (state 14).

Code Snippet:

1: 2: 3: 4: 5: 6: 7: 8:

Server returned status code 550 - Mailbox unavailable. The server response was: 5.7.1 Unable to relay for [email protected] Exception Details: Message: Mailbox unavailable. The server response was: 5.7.1 Unable to relay for [email protected] Type: System.Net.Mail.SmtpFailedRecipientException Stack Trace: at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at Microsoft.Exchange.Tools.ExRca.Tests.SmtpMessageTest.PerformTestReally()

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Answer : 5.7.1 Unable to relay; Mailbox Unavailable; new domains; Exchange 2003

Ok - it's fixed.

So, I focused in on a lot of stuff in this, but here is the proper fix.

telnet localhost 25 from the Exchange server.  Do a mail test to the affected domain:
-ehlo
-mail from:[email protected]m
-rcpt to:[email protected]  
UNABLE TO RELAY

That's the focus point.  I initially focused on on the
-relays
-antivirus
-reboots
-recipient policies
-etc... they are all distractions.  Your core issue is that the exchange server cannot figure out where to mail stuff to on its own (how it managed to deliver mail from OL client to the external domain name is beyond me, but that is the error to go on).

So, from there, you know the metabase is corrupt.   You know this because according to KB 895853 , page 4 of 8, there is a bullet point that reads DS2MB metabase key is corrupted (out of the many possibilities for SMTP error 5.7.1).    

Microsoft has a tool, called ExMetabaseCheck which will run, find errors, and near the end it will let you reset both the key and SMTP. Just let it do it.  That's it. Fixed.

Thanks for all of you who contributed... although really this post was more like a blog.  Hope it helps in the future.