active sync for iphone and exchange 2003

I currently have one exchange 2003 standard server with active sync to sync to iphones. i just installed a second exchange 2003 enterprise. i will be moving all mailboxes from exchange 2003 standard to exhange 2003 enterprise. do i need to buy/install another ssl certificate on the exchange 2003 enterprise server? i hope to get both servers working complete with active sync before i move all mailboxes over and decommision exchange 2003 standard server.\

thanks