We have an exchange 2003(installed in a win 2003 AD server) that we want to replace with exchange 2013. my question is: can I setup exchange 2013 without affecting the older version? I'm not interested on moving the mailboxes to 2013. just want to know if there are any issues having both of them at the same time and operating independently from each other.

here more detail about the environment:

1. exchange 2003 installed in a 2003 AD server
2. 50 mailboxes in production
3. Win 2008 AD
4. Most users are (100+) are on Exchange online services (Microsoft Office 365)

the goals are:

1. Install 2013 in a mix environment with Office 365.
2. Current mailboxes in old exchange server will not need to be migrated. they will be retire with the server.
3. Retired old exchange 2003 server

Thank you

Simon

If you try and run the setup for Exchange 2013 (assuming it will be on a member server in the same domain as Exchange 2003), it will detect Exchange 2003 is in use and stop at that point.  What you're asking is not possible;  you can have Exchange 2007 or 2010, but not 2003.

You could move all users to O365, retire the Exchange 2003 server and then introduce an Exchange 2013 server in a hybrid setup.