So here we are then - back on-line to continue this plight.
Thanks for those who have offered replies already, especially Geoff, most valuable. If I'd have known the BHT was an Exchange server bod I'd have just picked up the phone but as we've started down this path lets see if I can get a resolution.
Some more info for the assembled knowledgable ones.....
All was working well with one laptop, one desktop and one MDA (winows enabled smartphone), all with the same Exchange server account, new mails in, mails out, contacts added/removed and ditto calendar. Update something on one and its replicated on the other devices.
Then I came along and configured a new laptop, installed Office and configured Outlook by what I thought was replicating the settings of the retiring laptop. And now the following occurs:
When new laptop is used, send/recieve results in duplicates emails.
Neither MDA or Desktop see any mails picked up by New laptop.
When new laptop is not used Desktop and MDA work fine - so I know its something I've done/not done
As far as I can see Outlook web isn't utilised here - it looks for all the world that the new laptop is collecting mails and then removing them from the server as a POP account would in default mode but I don't see anything configuration for leaving copies on the server.
Additionally what is the duplicate mails stuff all about? Has it somehow got itself all confused by using a local profile in addition to an exchange server account?
Addendum: We cannot go back to the old laptop to re-check configuration as the owner when he thought he had a working resolution de-commissioned it ready for the scrapheap