Talks have continued between the postal workers' union and Royal Mail, as a 48-hour strike over pay and job cuts disrupts service.
Postal workers will return to picket lines on Friday
Communication Workers Union (CWU) members began the first of two walkouts at noon on Thursday.
The union said it remained "hopeful" but another two-day strike is set for Monday, adding to the disruption.
Meanwhile, Unite, which represents 12,000 managers, has struck a deal with Royal Mail on pay and pensions.
It has agreed a pay rise of 7.3% over two years - but has also accepted the replacement of the current final salary pension scheme with a "career-average" scheme instead.
Royal Mail had previously denied that it wanted to alter the pension scheme in this way.
The union will now work with Royal Mail to help modernise and secure the future of the business.
The company is likely to exploit the contrast between the approaches of the two unions.
CWU members returned to picket lines on Friday and said support for the strike had been "overwhelming".
But Royal Mail rejected such claims, arguing that in some places up to 90% of workers were working "as normal" and that 35,000 had come to work in the strike's first day.
The union plans to stage rolling strikes each Monday - starting this Monday at 0300 BST - until the dispute is resolved.
The dispute centres on the union's refusal to accept a pay offer of 2.5% as well as modernisation plans, which it believes will threaten about 40,000 jobs.
Royal Mail said it was "hugely disappointed and extremely concerned" that talks had failed to reach agreement.
A spokesman said: "The union continues to table unrealistic and unaffordable proposals that fail to deliver the flexibility and efficiency we so urgently need if we are to compete in today's challenging market place."
The company fears loss of business because of strikes.
CWU general secretary Billy Hayes, meanwhile, criticised the government for showing "complete disinterest" in the dispute.
"This is a company that they own and they seem to have no interest whatsoever," he said.
The government says it is up to the union and management to resolve the strike.