An online mailer that was emailed to customers signed up to PB Technologies revealed a "gross error of judgment" from a staff member.
The email sent on Sunday showed an online page with a broken image link. Instead of showing an image or graphic, it showed alternative text or the file name, which was "Nigger Line 780", suggesting the image or graphic should have showed a black line.
A PB Tech spokesperson responded to the error, saying the company was aware of the mistake and was shocked by it.
"Upon investigation, it was found that a junior member of staff made a gross error in judgement," the spokesperson said.
"PB Tech is a 100 percent New Zealand-owned, multicultural business with over 500 staff, and this incident does not reflect the values or views of the company. This was an isolated event and will not occur again."
A screenshot of the blunder was posted online and was met with shock, some calling it a "terrible joke" and "that shouldn't even be acceptable as part of internal stuff [even if it isn't] intended to be sent out".
PB Tech says it acted quickly to address the issue.
"We have taken immediate measures to address this incident internally, including but not limited to a keyword filter on our in-house mail platform.
"Additional processes for checking all customer communications before they are sent have been implemented. Disciplinary action has been taken, and further training will be provided for the staff member involved."
PB Tech claims to be New Zealand's largest computing and IT retailer and has at least 10 stores nationwide.