Dont use your NTL account and move over to your own account (buy a website or something), or get a free one from someone else.
Sounds like a crap reply i agree, but as everyone seems to complain about NTL's e-mail anyway then it may be a good idea. I have my own email account from my own website which isnt published anywhere on the site and i havent had 1 spam message in a long time.
Norton do an Anti-Spam product as well and there are freeware spam filters like Popfile (see here -
http://popfile.sourceforge.net/) which can do a similar job, but require a POP3 account.
Good luck.