Posties are predicting job cuts after New Zealand Post said it was considering halving the number of days mail is delivered because of the decline in the amount of mail it handles.
New Zealand Post says immediate changes are needed to cope with "irreversible" falls in postal revenue.
In a letter to State Owned Enterprises Minister Tony Ryall, NZ Post chairman Michael Cullen said the greatest threat to the company was the rapid drop in mail volumes caused by the public's shift to email.
Dr Cullen was seeking urgent amendments to the Crown agreement, the Deed of Understanding, which said the company had to run a delivery service six days a week at a standard cost.
Communications and Information Technology Minister Amy Adams, who would have to approve any changes to delivery days, said she accepted New Zealand Post's business had changed considerably over the years. Any proposed changes to the deed would have to go out for public consultation.