I have several email accounts that I view on my Nexus, but one a btinternet email address keeps downloading the same emails over and over.

None of the other accounts have this problem.

Also does anybody know of a better email program than the one shipped as default.

If you have several email accounts and they all have the same settings (ie. you don't have "Leave messages on server" or similar checked) and one behaves differently from the others, it could well be a problem at the server end. Have you tried downloading mail from the same account in Outlook or Thunderbird (or equivalent)?

As for better email programs, I find the ICS email app pretty damn good so haven't done much research into others, but I know K9Mail comes highly recommended.

The mail accounts all work fine in outlook and on a HTC HD2 even the btinternet account. So I have ruled out the accounts.

I will give your suggestion a try.

Does the Nexus email app have the same problem as the Note mail app, where Hotmail set up via Exchange Server doesn't download the email in HTML so you have to click 'load more details' on every email you open?