New Zealand Post says parcel volumes are continuing to grow, up by 4% per year, but the rise can't arrest a steep decline in overall mail volumes.
Chief operating officer Ashley Smout said New Zealanders are ordering more items online, which has bolstered parcel volumes.
But New Zealand Post mail volumes continue to fall at a rate of about 8% per year, or about 40 to 50 million fewer items.
Mr Smout said the decline was the biggest ever in 2013, compared with between 5% and 6% in the past.
He said the company is meeting this challenge with more advanced sorting procedures to reduce the amount of manual sorting and providing posties with different modes of transport.
Late last year, New Zealand Post said that between 1500 and 2000 jobs would go as part of its strategy to maintain a viable business.
Mr Smout says mail volumes are expected to keep falling in New Zealand as businesses encourage their customers to move to online statements and bills.