Although my emails come through an exchange server they are currently stored
on my local machine. I now want a copy to remain on the server so in email
account settings if I select Cached Exchange Mode and will this copy my
emails back to the server?
My main query, will this also copy any POP3 emails that I have stored
locally up to the server?

Mark_Vader wrote:

Although my emails come through an exchange server they are currently
stored on my local machine.

In a PST?

I now want a copy to remain on the
server so in email account settings

Change your delivery location to the Exchange mailbox.

if I select Cached Exchange Mode
and will this copy my emails back to the server?

Certainly not. Cached Exchange mode has nothing to do with it.

My main query, will this also copy any POP3 emails that I have stored
locally up to the server?

If you copy them, of course. Future incoming POP mail will get store on the
server unless you create a rule to move it elsewhere.
--
Brian Tillman