Telecom is again warning a security threat has compromised some of its customers' Yahoo Xtra email accounts.
On three separate occasions last year, Telecom customers had their email accounts used to send out malicious spam, including almost 90,000 accounts in February.
Telecom, which uses the Yahoo Xtra email platform, says it has been told there have been unauthorised attempts to access users' email accounts.
It says there is no evidence that account information has been used and customers have not reported any problems.
It says Yahoo will be blocking the compromised accounts until affected customers reset their passwords and secure their accounts.