Question : Introducing Exchange 2003 server into a Single Domain with a Exchange 2000 domain Controller.

Long story short....I want to remove my old exchange 2000 server because of hardware issues. I purchased a new server which came with Windows 2003 already loaded. As I began to consult technicians I found that Exchange 2000 would not run on Windows 2003. I purchased Exchange 2003 for the new server. Now I upgraded my PDC to Windows 2003 also and correctly followed the process of Forrest Prep & Domain Prep (I only have one domain) and brought the PDC up with few problems. By the way my  Exchange 2000 box is also a DC. I loaded Exchange 2003 on my new server and joined it into the domain as a DC with the Exchange 2000 server being the master database(I did the preps in the correct order and also did the Exchange 2003 Management correctly on the exchange 2000 server). In addition I also have Mailsweeper for SMTP loaded on the Exchange 2000 box as well. I changed the Exchange mode from mixed to Native since I have no old Exchange 5.5 or Nt 4.0 servers. Everything appears to be in order but the Exchange boxes will not communicate with each other. I successfully moved a couple of mailboxes but the ones on the new server cannot send or recieve mail. On the 2000 server I am getting this error message every couple of hours in the application viewer with Types 1 thru 4. They are as follows-
Event Type:      Warning
Event Source:      MSExchangeMTA
Event Category:      Directory Access
Event ID:      9302
Date:            4/3/2006
Time:            2:23:34 PM
User:            N/A
Computer:      EXCHANGE
Description:
The transport configuration type 4 for the directory entry CN=MICROSOFT MTA,CN=EXCHANGE,CN=SERVERS,CN=FIRST ADMINISTRATIVE GROUP,CN=ADMINISTRATIVE GROUPS,CN=HBCONET,CN=MICROSOFT EXCHANGE,CN=SERVICES,CN=CONFIGURATION,DC=HBCONET,DC=COM is not one of the supported values. Reconfigure the transport configuration type in the identified directory entry. [BASE IL OPERATOR 24 217] (8)

Any Help would be appreciated,
Chris

Answer : Introducing Exchange 2003 server into a Single Domain with a Exchange 2000 domain Controller.

The Exchange servers pass information between themselves on port 25.
Therefore if you have modified your existing server's SMTP server to operate on a port other than 25, then the email and replication information will not flow.

You have two options.

1. Put the original server back to port 25. You could put a second internal IP address on to the server, then reconfigure the other application to use that second IP address, adjust the firewall etc to send email to the second IP address. (That is how I would have done it in the first place - I don't like changing the ports of applications - and this is a clear example of why).

2. Reconfigure the new server to use the different port so that the servers can communicate on the same port.

Simon.