9 times out of 10 the solution with Outlook Express problems is simply to delete the account and then create it again. (You're only deleting the settings; you won't lose any existing mail).
Go to Tools > Accounts > Mail (tab)
Click on the name of the account to highlight it.
Click 'Remove' and then 'Yes'
I suggest closing Outlook Express and then reopening it (or even restarting your computer) to ensure that the settings have really gone.
Then go to Tools > Accounts > Mail (tab) again.
Click on 'Add'and 'Mail'
Then configure your account account:
https://help2.talktalk.co.uk/email-settings-imap-pop3