I'm working on migrating a companys Exchange 2003 to an Exchange 2007 SP3 server (installed on W2K8R2). I'm using this guide to help me along http://www.msexchange.org/tutorials/Transitioning-Exchange-2000-2003-Exchange-Server-2007-Part1.html
I've run in to this weird issue that I'll try to explain below.
Exchange 2007 installed fine (after SP3 was released) and I could create users and mailboxes on it. Mail flow worked like a charm between the two servers both internally and externally. the installation is at the moment pretty default, although there is an anti-spam 3rd party provider configured who recieves all email for the company and then forwards it to the Exchange 2003 server. There is no smarthost or external scanner configured for outgoing email (at least not by default). The company has a German office who sends as company.de and the default user sends email as company.dk (Danish company).
So this is what happened. A week or so after the initial installation and tests the German users (who send as email@example.com) started recieving delay messages and finally delivery errors on about half of their external emails. All users mailboxes are still located on the old 2003 server. So I went in and configured a smarthost so that all external email was send through this smarthost, I configured it on both the old 2003 and the new 2007 server. The problems the German users had went away then. But then another problem occured, the comunication from Exchange 2003 to Exchange 2007 went down (to be precise it was replication of public folders and delivery of emails to a test user located on the Exchange 2007 server that went down). I could see the queue just held the messages as they could not be delivered to the smarthost who obviously didn't know what to do with them. So I had to remove the smarthost and then the mailflow (smtp) started working again, but the Germans started getting errors again. So now I'm back with the smarthost and have put the project on hold as I can't perform any testing before this problem is resolved.
I've confirmed that SPF records are configured correct for the two domains, the only thing missing is a PTR record for the Exchange 2007 server.... are Germans really using PTR??
So my question is this (hence the title of the post).
Users with mailboxes on the Exchange 2003 server, does their mail flow through the Exchange 2007 server when sent? (it seems to me that the above problems point to this)
On a broader scale, could anyone please explain the mailflow when you've got an Exchange 2003 and an Exchange 2007 server installed and mailboxes created on both server (both internal and external mail). I would have thought that they minded their own business and just passed internal messages to each other ....but I might be wrong.