Student emails have been suspended at Mt Albert Grammar in Auckland after a security breach led to porn being sent to every student.

An official message was sent to parents on Monday night apologising for any offence caused.

Principal Dale Burden said they believed the culprit was most likely to be a student at the school and if so that amounted to serious misconduct.

The school was first alerted by a parent who saw the email which contained a link to a pornographic image.

It is believed the hacker used a fake Gmail account to send the email to every student on the Mt Albert Grammar database.

Staff at the school were not sent the pornographic image.

Staff were alerted to the breach in an email on Tuesday advising inappropriate pictures had been sent to each student in the school.

Burden said investigations were continuing and measures have been taken to avoid a similar breach in the future.

Student emails won't be back up and running until the school is sure it is secure.