Telecom has acknowledged on its website that some emails sent by its YahooXtra customers to TelstraClear customers are bouncing back.
The company updated the "service status" on its website to acknowledge the problem more than a day after it was first approached by BusinessDay and advised of complaints from readers.
Telecom said it was working closely with its outsourced email provider, Yahoo, and Telstra to resolve the issue.
Both parties had made changes to their networks and it was checking whether that had fixed the problem.
Telecom previously said it had decided not to alert customers to the issue as it was "fairly minor and resolved very quickly with a limited number of customer calls".
Not all email to TelstraClear customers was bouncing back. Fairfax NZ