An Air New Zealand flight attendant has been sacked after mistakenly sending a "highly derogatory and offensive" email about an Air New Zealand manager to the man himself.

Grant Fife, who worked for the airline for 21 years, is fighting for reinstatement.

The trouble arose last September after Air NZ performance and development manager Phil Callahan sent an email to flight attendant Dale Kiely about an insurance claim. A copy was also sent to Mr Fife.

Thinking he was writing only to Mr Kiely, Mr Fife mistakenly responded to Mr Callahan, describing him in "highly derogatory and offensive terms", says an Employment Relations Authority ruling issued yesterday.

Mr Fife was dismissed in March for serious misconduct.

He has appealed to the authority against his sacking, saying the penalty was too harsh, especially for someone with his experience in the company.

Air NZ would not reveal the contents of the email but the authority report said it was vitriolic and deliberately constructed to be offensive.

Authority member James Wilson ruled that the sacking was "harsh", but said Mr Fife would not be reinstated before another hearing was held.

Mr Wilson noted that Mr Callahan was not meant to see the email, and that Mr Fife had apologised for any offence caused.

Employment lawyer Andrew Scott-Howman - who was not involved in the case - said workplace fallouts over misdirected emails were common, but very few resulted in sackings.

"I find it surprising that someone would be suspended over an email," he said. "It's not inconceivable, but it would have to be at the high end of the scale or serious misconduct. It would be a defamatory statement."

He said the penalty for misconduct could depend on several factors, including how offensive the email was, the employee's past record, and the type of workplace he was in.

Mr Fife had asked to be allowed to return to work urgently so he could keep up with health and safety requirements.

But Mr Wilson said it would be easier if Mr Fife was not reinstated.

His full complaint would be heard this month and a decision would be made soon after the hearing.