No. You can’t introduce Exchange 2007 into an existing Exchange organization while an Exchange 5.5 server still exists in the organization. If you run Exchange 5.5, you must first upgrade to Exchange 2000 Server or Exchange Server 2003, effectively Exchange native mode. After you move the mailboxes to an Exchange 2000 or Exchange 2003 organization, you can move the mailboxes to Exchange 2007 via the Exchange 2007 GUI if Exchange 2007 and the Exchange 2003/2000 installation are in the same organization or by using the Power Shell Move-Mailbox command for cross-organization migrations.
You can copy Exchange server 2003′s ESEUTIL to another machine, along with the database to run. First, create a temporary folder on the computer that you want to run the defrag on. Then, copy the eseutil.exe, ese.dll, jcb.dll, exosal.dll, and exchmem.dll files from the Exchange 2003 computer’s ExchsrvrBin folder to the temporary folder, along with the database and streaming files. At a command prompt, change the directory to the temporary directory folder you created and copied the files to. Finally, run the Eseutil command from this folder against any databases that you copied from the Exchange 2003 computer.