An IT security specialist says Telecom could lose customers as a result of the continuous hacking of its Yahoo Xtra email accounts.
Yahoo has said it identified a co-ordinated effort to gain unauthorised access to the accounts last week, forcing the company to lock the accounts of some users.
IT security specialist Andy Prow said the latest attack seeks information such as credit card details and contacts from the most recently sent emails.
Mr Prow said some Yahoo Xtra emails are being automatically blocked or sent straight to recipients' spam folders because the email accounts have become synonymous with spam and viruses.
He said email is critical for businesses and Telecom could soon start losing customers as firms look for systems they can rely on.