We are starting a pilot program with google apps and are having an issue with exchange users being able to send to the google apps pilot users. We have setup dual delivery so that emails are received in both locations. Emails sent from exchange are sent back to exchange. All other outside emails are being routed to google as we have set emails to go to their servers first based on mx records. How do we configure our Exchange 2003 to not take the lazy way out and do an mx lookup instead?

If the users exist on Exchange, then Exchange will send to them. Nothing you can do to stop that. Exchange will NEVER look at DNS records for a domain that it knows it is responsible for. You will have to configure Exchange to share the SMTP address space: http://support.microsoft.com/kb/321721 That may not catch everything though, because the SMTP address space isn't really used internally other than a resolution method. Therefore users replying to old emails sent by those users now on Google Apps will find their emails are going back to Exchange mailboxes. If you have removed the mailboxes then they will bounce. Nothing you can do to change that, other than setting up a contact to send the email externally, but that would need a completely seperate domain, again because Exchange will treat the same domain as internal. The share SMTP address space methods basically depend on the SMTP address not existing anywhere in Exchange - mailbox, group or contact. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.

I made those changes this morning and all of our gmail users are now able to receive email from the exchange. However, our exchange users are no longer receving any emails from anyone.

What did you do exactly? The MX records would probably need to point to Exchange, so that Exchange sends the email back to Google. I don't think Google have a way of getting the email to your Exchange server in a co-existance environment. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.

I used the link that was in your first reply and used Method 1.

did you check that your mx records are set up properly at www.unlocktheinbox.com/dnslookup/mx/ ?