The first email was sent on Friday.
In a statement, Transport Minister Phil Twyford said: "Obviously this isn't ideal but people make mistakes.
"I'm sure the staff involved feel badly about the mistake and they will make sure it doesn't happen again."
But National's cybersecurity spokesman Shane Reti said privacy breaches are becoming a pattern from NZTA.
"Twyford needs to step up and take charge of his agency," he said, adding that this was another example of NZTA failing under his watch.
He said accidently including email addresses in a broadcast email was a "cybersecurity 101" failure, and many sensible organisations have filters that check exactly this sort of thing.
"The Minister needs to own this mistake and urgently cyber credential NZTA."
The NZTA spokesman said the agency takes any breach of privacy "very seriously".
"We regret that this has occurred and steps have been taken to ensure that it is not repeated, including requiring an additional review step before the distribution of such updates."
A spokesman for the Privacy Commissioner said although the breach was "far from ideal," the information disclosed was at the less serious end of the range of personal information.
"While there may be a possibility of harm to an individual resulting from this breach, it is also at the low end of probability."
The privacy breach comes just months after NZTA was forced to notify the Privacy Commission about a lost USB drive, which was misplaced somewhere between Auckland and Wellington late last year.
As well as notifying the Privacy Commissioner, NZTA also launched its own internal investigation.
That investigation has finished and an NZTA spokesman said the report, and its recommendations, would be finalised soon.
But he confirmed the USB stick had still not been found.