Telecom is contacting some Xtra email users as it applies the latest in a series of security enhancements to the Xtra emails.
An additional encryption setting called `Secure Sockets Layer' (or `SSL'), will soon be the new standard default connection for all Yahoo Xtra mail accounts.
Telecom said today it would be helping users who access the service via a third party email client, such as Microsoft Outlook for PCs or Android for mobiles, to update their settings.
SSL secured a user's information and email messages, making communications more private as they moved between the user's browser/device and Yahoo's servers, Telecom retail chief executive Chris Quin said.
But it was important for customers take their online security as seriously as possible, he said.
"We're continuing to look at what we can do to enhance Xtra mail so our users can have more confidence in the service to get on and do more online.
"That said, while we'll do all that we can to keep customers protected via their email portal, these security updates will not prevent the ongoing circulation of spam,'' Mr Quin said.
"Nor will it prevent Kiwis from clicking suspicious links contained in emails which can perpetuate spammers' activity. Together, we need to work to keep all of us safe online.''
Email users should be careful to regularly update account settings with a strong, difficult to predict password and refrain from using the same password for their online banking, their email and their Twitter account.
Emails containing suspicious links should be immediately deleted, even if they're received from known and trusted contacts, Mr Quin said.