Customers with a Vodafone email address will have to switch at the end of November, when the telco plans to axe its email services after 20 years.
Email addresses affected include its Clear and Paradise services.
Vodafone had about 200,000 to 250,000 active email users but many operate dual email accounts, a Vodafone spokesperson said.
The accounts would be switched off on November 30, however, Vodafone has promised customers it will automatically forward emails from the closed accounts to a new email of the customer's choice, for as long as they are a Vodafone customer.
The telco was encouraging users to set up a free Microsoft or Google email account.
Vodafone New Zealand consumer director Matt Williams said customers had told the firm its email service was not delivering on expectations.
"That's simply not good enough for us," Williams said.
"We've made the decision to close the service and connect customers who need a hand setting up a new account to the email experts, Google Gmail and Microsoft Outlook."
The move follows issues over the last few months including high levels of spam and delayed mail.
The company said many of its customers already had alternative web-based email services "with greater functionality" such as Gmail and Outlook, which were easy, secure and efficient.
Vodafone would email affected customers about the closure and giving information on how to set up automatic forwarding and a new email address.
The communication sent to vodafone.net customers said Vodafone had tried very hard to fix the problems it had faced "with little success due to the age of the platform".
Email platforms affected: