A security update announced on Telecom's Yahoo! Xtra email service on Monday should have been there in the first place, an IT security expert says.
Telecom was forced to lock the accounts of some users after tens of thousands were hacked in January.
The company is now beginning to improve security with a new encryption setting that will make communications between accounts more private.
But IT security specialist Andy Prow says the improvements are well overdue.
"The fact they're putting it on is good. It's a must-have - it really should have been there since day 1, but it's good that it's being applied now. So therefore, it's a step forward in security. There's no way that that is all that needs to be done."
Mr Prow says users of the Yahoo! Xtra service need to vigilant against cyber attacks.
