Vodafone will axe its email services in a move that will impact between 200,000 and 250,000 customers and could increase the power of Google's Gmail.
Vodafone will turn off its email accounts, including Clear and Paradise accounts, on November 30 and will instead encourage customers to set up free email accounts with either Google or Microsoft.
The decision follows months of problems with high levels of spam and delayed mail.
Telecommunications Users Association chief executive Craig Young said many of the people who would be impacted would be older people who were early to get onto the internet, and he feared some of them would face a steep learning curve.
Both he and his parents had Clear accounts, he said. "The younger generation probably have Gmail and Hotmail accounts so they won't be so affected."
Vodafone has promised customers it will automatically forward email from their closed Vodafone address to a new email address of their choice for as long as they remain a Vodafone customer.
That meant customers would still be able to use their existing email addresses as a user name for any other service – such as internet banking – they were signed up to, it said.
Young said the closure was not surprising but the notice Vodafone had provided was surprisingly short.
Gmail was already "the most pervasive email platform in the world" and Young said there were concerns about the impact its growth could have on privacy.
"We know if we sign up to use it that we are letting Google have access to the information that is stored there." Young said he would also not be surprised if Google introduced a fee for using Gmail "at some point".
Vodafone consumer director Matt Williams said customers had told Vodafone its email service was no longer delivering the sort of experience they needed.
"That's simply not good enough for us here at Vodafone" and was why it had made the decision to close the service down, he said.
All customers would receive an email from Vodafone with the "news of the closure, support around how to set up auto-forwarding, and an introduction to Google Gmail and Microsoft Outlook", he said.
Spark also experienced years of problems with its Xtra email service after outsourcing it to United States' internet giant Yahoo in 2007.
It also considered simply stopping providing email, but instead decided to take a different tack, this year migrating its 800,000 email users to a new service provided by Auckland email specialist SMX.