TalkTalk customers are currently seeing high volumes of old emails and duplicate emails appear in their accounts; this is both webmail and external clients (e.g. Outlook)
CPW Network Engineers are investigating the root cause of this issue, we'll update you as soon as we can.
http://www.talktalkmembers.com/forums/showthread.php?t=18397
http://www.talktalkmembers.com/forums/announcement.php?a=29