Ok, using IMAP on 3 email accounts. I use Outlook for Mac 2011, iPad Mail and Android Mail to access. Messages download fine - no duplicates. I read a message, thats fine, if I then DELETE the message it is moved to the TRASH folder and marked as READ.
Next time the mail programme accesses the webserver a new, DUPLICAT copy of the deleted email shows up in the TRASH folder but this one is marked UNREAD.
This also happens if I read an email and move it to another folder in the mail programme I happen to be using.
As this is happening on 3 different platforms and 3 different email software programmes, the only common factor is TalkTalk's Webmail server.
THIS DID NOT HAPPEN BEFORE THE SOFTWARE UPGRADE TO WEBMAIL.