In Outlook, goto Tools > Email Accounts. Select "VIew or change existing email accounts", then Next. Highlight your account, (ISP), then click the Change button. In the next window, click the "More settings" button.

In the next window under Delivery, either remove the tick in "Leave a copy of messages on the server", or leave that tick, and select one or the other or both of the next options, ie;

Remove from server after xxx days, (choose a period),
Remove from the server when deleted from "Deleted Items".

Then OK out, goto Next, Finish.

Then from Tools > Options, under the "Other" tab, place a tick in the "Empty the Deleted Items folder upon exiting". Apply then OK out.

Hopefully that will stop the server sending you duplicates.

Not sure about your next question. Microsoft Express is an email program I haven't heard of.

Personally I don't use either Outlook or Outlook Express. They both have good features, (Outlook is better for corporate, business use), but some years back Outlook and OE suffered from bad press with vulnerabilities for viruses, etc, and they have never really recovered.

I use Netscape 7's email program. It's old and grumpy, but I still like it. Other people here will suggest Mozilla's Thunderbird email program, (the companion to the Firefox browser), and I undestand it is much like Netscape's email, but newer, sleeker, faster, etc.

But there are others, eg Eudora, which I have never tried.

It's up to you really.

Good luck,