Members of the Communication Workers Union (CWU) in Royal Mail have overwhelmingly endorsed the 2005 pay agreement.
The deal, which includes above inflation pay rises, was backed by a margin of 11 to one.
CWU deputy general secretary, Dave Ward, said: "I am naturally very pleased our members have given their overwhelming support to this agreement. We were confident they would regard it as a decent settlement and now everyone will receive above inflation increases in their basic pay."
This agreement is just one plank of the union's campaign to improve its members' pay, terms and conditions.
"We have made a commitment to fundamentally review everyone's employment package and we will fulfil that pledge," Ward said. "The ultimate aim will be to deliver further improvements to basic pay and enhance their working environment."
The overall cost of the deal is about £122m to the company.