Friday, December 13, 2013

Routing Group Connectors - There is currently no route to the mailbox database

When performing an Exchange 2003 to Exchange 2010 migration, mail flowing between the two servers using a routing group connector was not working.  When relaying an email to the Exchange 2010 server for a user mailbox residing on Exchange 2003, the email would simply sit in the queue and not send.

The following error was experienced:

There is currently no route to the mailbox database

This can be seen in the message log with "Get-Message | fl"

 The messages simply sat in the Unreachable queue on the Exchange 2010 server.

This error generally means no routing group connector was made between the two servers.  However I confirmed the routing group connector was created by Exchange Setup automatically.

Next I removed these routing groups and recreated them with new ones through PowerShell:

After recreating the routing group connectors you must restart the "Simple Mail Transfer Protocol" service on Exchange 2003 and the "Microsoft Exchange Transport" service on Exchange 2010.

This still did not resolve the problem.


Next I started checking permissions of Exchange container objects in the configuration partition within Active Directory against a default install of Exchange 2003 in a test lab.  I noticed that permissions on the Exchange 2003 object in Active Directory was no longer inheriting from the Administrative Group/Servers Container.

After re-enabling inheritance using ADSI Edit over the Exchange 2003 server object, this resolved the issue.


  1. AWWW YISS you just saved me. I did this on my previous Exchange migration but completely forgot about it. Had the exact same issue as you: 2010 > 2003 mailflow wasn't working but 2003 > 2010 was. Recreated RGC, restarted services, created the smarthost on the SMTP Connector on Ex2003 versus using a Default Virtual Server.


  2. DUDE! 4 hours of digging and banging my head into my desk and you saved me with a single check box, Thankyou!

  3. Thanks! Saved me a lot of trouble. One Legacy 2003 server, out of 5 servers, was missing the "enable inheritance". Reset the permissions and restarted SMTP and Transport services, and mail flowed.

  4. Thnx man. First i try remake RGC like u , but what is not resolve the problem. After make inheritance on the old server container -everything ok. Unavalible(no route to mailbox database ) massage queue cleared .

  5. Thanks!! I was troubleshooting for a couple of hours! And this thread Fix It! Thanks!!