[nostra]

go into thunderbird...

go to tools > account settings > outgoing server (smtp settings)

remove the username in there if there is one and untick username and password

you should then be able to send mail ok

hope this helps

thunderbird automatically ticks username and password as default it appears even though there is no username in there and something that has happened while upgrading the ntl smtp servers has caused anyone with these settings ticked to fail :S