Right, here goes.

At work we are going to migrate from Exchange 2003 to Exchange 2010 by installing a new server with 2008 R2 64bit SP1, and Exchange 2010 SP1 obviously.

I have setup a test environment, with an Exchange 2003 server and a test install of Exchange 2010 and I can move mailboxes between both servers (both ways) easily.

Outlook works fine and senses that the mailbox has moved and reconfigures itself, and loads the moved mailbox fine.

Now for the problem, once the mailbox is moved it is not possible to send an email to the moved mailbox. The GAL still shows the mailbox and I can select it and hit send and the email goes from the outbox, but it never gets to the other mailbox. Same problem emailing from the moved mailbox back to exchange 2003. Basically message routing is not working and its something I think I need help fixing.

Before anyone mentions it, migration from Exchange 2003 to 2010 is now a supported upgrade path (never used to be).

The message tracker in Exch 2010 shows.

3/22/2011 6:39 AM test.local

The message is pending in the queue 'TEST\Unreachable'. The last error was 'There is currently no route to the mailbox database.'.

So, answers on a postcard please.

We had the same issue on our migration, mails going "cross infrastructure" would just sit in a queue on the hubrelay box

Ill ask around to try find out what the solution was.

Thanks Colin, need to make sure it all works before doing it live.

Where is your CAS Mannyo?, all access to a mailbox database in Exchange 2010 is routed via the CAS, you also need to have Digest authentication installed in IIS on all of your Hub Transport servers.

Migrations from 2003 have always been supported, inplace upgrades are not however.

Edited 23 March, 201115 yr by fluffmeister

Am struggling to find out the cause and solution.. which always seems to be the case with projects put in by third parties..

All ive been able to gather is we had issues with expanding distribution groups, and mention of permissions on the receive connector on the 2010 end.. something to do with needing to allow anonymous access.

Fluff will fix it for you.. hes suppost to be good at ex2010

The receive connectors do need anonymous access enabling Col. Where people get it wrong with 2010 is typically on the CAS, there is a major arcitecture change from 2007 and all mailbox access is routed through the CAS. Hub Transport servers deal with the physical routing of mail and mailbox database locating, the CAS deals with MAPI authentication now as well as non-mapi.

I was mainly kept away from our implementation.. that and i have a hard time trying to keep 4500 mailboxes and replication from destroying a mere 12 SATA disks.... all because someone read that 2010 runs well on sata