New Zealand Post has begun consulting staff over plans to shed up to 100 positions from its mail centres to match the drop in letter volume. The centres currently employ 1,800 people.
The number of letters handled by New Zealand Post dropped by 30 million or 6% in the second half of last year as the economy slowed.
The state-owned company says general mail is down by 10% to 12% on last year.
Postal services chief executive Peter Fenton says New Zealand Post has begun consulting unions and workers at the city-based mail centres and other administrative staff over reductions to the overall workforce.
Mr Fenton expects the equivalent of 80 to 100 full-time jobs to go across the country.
He says there are a range of options for the reductions including cutting work hours, part-time shifts, voluntary redundancy or compulsory redundancy.
The Postal Workers Union says it will not let New Zealand Post use the economic crisis as an excuse to lift workloads.
The union's southern region president, John Maynard, says New Zealand Post might be tempted to follow other employers and use the economic situation to reduce numbers more than necessary.
"We've raised that with the company and it's something we'll be watching very closely - that we don't have too many redundancies and end up with the people who are left having to work harder."
Mr Maynard says workers accept the need for cuts, but want to negotiate over how they are made.