Postal workers have voted to accept a "ground-breaking" deal on pay, pensions and job security.
The Communication Workers Union said its members backed the agreement by 94%, paving the way for a 9% wage rise over three years and legal protections on their terms and conditions.
The union said it was a landmark deal, negotiated following members' support for industrial action at a time when the Royal Mail was being privatised.
Officials said the deal, accepted in a 57% turnout, signalled a "fresh approach" to industrial relations.
CWU deputy general secretary Dave Ward said: "We are extremely pleased to secure this ground-breaking deal with Royal Mail, which postal workers have overwhelmingly voted to accept.
"We have achieved extensive and unprecedented legally binding protections for employees that not only strengthen their job security but also shape the values and principles that the Royal Mail Group will operate under as a private organisation.
"The pay deal is at the very top of the range in either the public or private sector and the commitments to legal protections and industrial stability changes the dynamic of privatisation. The agreement bucks trends in UK employment and means Royal Mail, as a private company, cannot adopt the type of employment model and practices that are undermining workers everywhere.
"This agreement commits Royal Mail to an agenda for growth, rather than managing decline. There will be no tolerance for a race to the bottom on services and jobs and we believe this agreement will set the standard for pay, employment rights and services for the rest of the postal industry."
Postal workers will receive a 3% rise in pay and overtime rates, backdated to last April, a further 3% rise from this April and 2.8% from April next year.
Royal Mail chief executive Moya Greene said: "I am pleased that our people have voted in favour of the terms of the agreement. This is the first critical step to provide long-term stability and certainty for Royal Mail, our employees and our customers. Now the hard work starts.
"Working together, we will create a strong foundation for the continued success of our business."
The company said the agreement underlined the importance of its modernisation and transformation programme, adding: "This is one of the biggest transformation programmes in UK industry and it is changing every aspect of the way our people work. The agreement emphasises that efficiency is a prerequisite for growth."
Peter Harwood, Acas chief conciliator said: " I'm very pleased to hear about the CWU's ballot result.
"Having worked as an adviser with the Royal Mail and the CWU over a number of years, and more intensively over the last few months, I'm particularly pleased that mediation instead of industrial action is such a key feature of their new agreement.
"I hope the agreement will enable the company and the union to continue to successfully go forward together."