Re: the advice on settings, I've just tried to re-install my btinternet account on Outlook and it does not recognise the SMTP server setting given and doesn't work on the automatically populated one either.
Thanks Neil, but I did check the settings and they were rejected. Since this has worked for the past several years, including after password updates, I see no reason why they should suddenly need manual intervention. Whether the fault is at the BT or Microsoft end I cannot work out but it is very inconvenient.
PS. the BT mail system put your replies into the Spam box. When it cannot even recognise the BT Community as safe we have problems.