how do I configure phone so when I delete an exchange message from iphone it does NOT delete from my computer?

I have just upgraded from an Iphone 4S to a 5. I previously had the syncing set up so received email on the phone and exchange email on my PC. When i deleted messages from the computer it the message was also deleted from the phone but not vice versa, I.e. when I deleted from the phone the message was NOT deleted from the computer.

With my new phone when I delete from the phone it also deletes from the computer but I don't know how to change the syncing so it's set up as I had it before, i.e. delete from the computer deleted from the phone but deleting from the phone does NOT delete from the computer.

Can anyone explain how I change the syncing?

Thanks