Exchange 2010 and 2003 working togeher

I just joined an Exchange 2010 server to an existing 2003 domain/exchange environment.

The new 2010 server is working fine and I can transfer mailboxes to it but when I do those mailboxes cannot longer receive mail (internal or external). They can send out though.

Ultimately once I get all the mail boxes and public folders off of the 2003 server I will just redirect the MX records so they hit the 2010 box but right now I still have over 40 mailboxes on the 2003 server.

I was hoping I could stage this and move mailboxes one at a time but I need to make sure the users that move are fully functional on the 2010 server. I thought there was a way to have the 2003 server receive the mail but have it send the messages to the mailboxes on the 2010 server. Is that possible?

I have looked at the message tracking and when I message is received on the 2003 server for a user that is on 2010 it says – “Message Routed and Queued for Remote Delivery” but it never ends up in the user’s mailbox.

I have tried setting up receive connectors but I cannot get it to work.

If anyone can help with this or point me in the right direction it would be greatly appreciated.

Thanks in advance.