Norman wrote:

I have to ask, is there no work around?

As you mention, if he chooses to remove the messages from the server for one
machine, then of curse the other won't download them because they won't be
there. If he syncs his PST back and forth between the two machines, there
should be no problem.

Also uncertain to me is he referring to something like exchange server or
his ISP's?

The OP's talking about a POP/SMTP account.
--
Brian Tillman