if you set up email through exchange will that leave a copy in your in box.
With Exchange & IMAP, whatever you do on one device will be reflected on another. For instance, if you read an email and opt to leave it in your inbox after reading it via your iPhone, the message will still be in your inbox when you access your email via your computer.
if you delete it off the phone I'm looking for a way to leave a copy on the computer when i delete it off the phone.
Exchange is not like POP3 that pulls emails off the server onto the device you are viewing it on and where you have to select an option to leave a copy on the server. Think of Exchange mail as "cloud-based" and not local. An in-depth view of POP3, IMAP & Exchange can be read
HERE.