email quota filling up very quickly


New Email
We have recently changed host and created a new website entirely on a new domain with a number of new email accounts. Our previous domain however directs to the new domain so the emails delivered to it are being sent our new mail server. The problem is that the previous domain had a large number of email accounts on it and most of these are still receiving mail, but mostly junk, which is now being delivered to our new mail account. This is causing the mail server to fill up very quickly and we are being blocked by the host whenever our limit is reached.

Is it possible to stop the majority of mail delivered from the previous domain's mail account being delivered to the new one, BUT we need mail delivered to one or two of the accounts to still arrive.

How can I select mail delivered to a couple of the old mail accounts to be delivered to the new mail server and the rest not?