We just added a Exchange 2007 server to an existing Exchange site. I have moved a mailbox over and it connects fine, but I'm finding that the queue for the routing group between the two to be growing. Sometimes it'll wait 30 min and fill with 15 messages or so, and then all go through. I have deleted the routing group and created it again, at that time it works fine. But what would cause it to be intermittent like I'm seeing?

Hi, Firstly, as the messages can be sent to Exchange 2007 finally without changing configuration, I do not think that it is a configuration issue of Exchange Server. The issue can be caused by several factors, such as: 1. Poor Network performance at that time 2. Poor Exchange Server performance at that time 3. Poor DC performance at that time 4. DNS related issue 5. Some large messages need to be sent Nevertheless, as the issue does not occur currently, we do not have sufficient information to troubleshoot the issue. Therefore, I suggest you run ExBPA to do a health check and fix related issues if they exist. If the issue occurs again, you can attempt the following method to troubleshoot the issue: 1. On Exchange 2007, run Get-queue to check which queue the message stuck in. On Exchange 2003, you can use Queue Viewer by referring following article: How to use Queue Viewer to troubleshoot mail flow issues in Exchange Server 2003 http://support.microsoft.com/kb/823489 2. Please check if you send a message to local user in the same server, whether the message can be received immediately 3. Please check whether the Exchange 2003 and Exchange 2007 can telnet each other successfully through FQDN 4. Run Get-message |fl to check whether any large messages wait to be sent 5. Capture Network package between Exchange 2003 and 2007 to check whether any network latency issue exists. Mike