Thousands of postal workers turned out to "solidly support" a fresh strike which has ended tonight with millions of items of mail caught up in a huge backlog.
The strike was the third consecutive day of industrial action to hit the Royal Mail in a row over jobs, pay and modernisation.
The Royal Mail said 25% of its delivery staff turned up for work despite the action but the figure was disputed by the Communication Workers Union.
Officials maintained there was solid support from its 77,000 members involved
in the walkout and said the public was continuing to back the workers.
Thousands of delivery and collection staff braved pouring rain to mount picket lines outside mail centres.
Further action is planned next week unless marathon talks between the two sides produce a breakthrough.
The next 24-hour national walkouts, involving all 121,000 postal members, are scheduled for Friday, November 6 and Monday, November 9.
Negotiators from the union and the company are considering a series of proposals drawn up during talks chaired by TUC general secretary Brendan Barber.
The two sides are aiming to resume negotiations early next week.
CWU general secretary Billy Hayes said: "It is not necessary for this strike to take place and the union remains focused on reaching an agreement. We hope that Royal Mail will also now be equally focused.
"CWU is determined to reach an agreement or make enough progress to call off strike action next week."
Mark Higson, managing director of Royal Mail condemned the union for calling more strikes, warning it would "distract" from the peace efforts.
"The CWU's irresponsible behaviour underlines just how muddled and confused the thinking of the union is - and how little it really cares about customers or the future of the UK postal service.
"Thanks to the efforts of all our people who continue to work... we will be able to limit the effect of the current strikes and expect to get any delayed mail to our customers by early next week, well ahead of the CWU's next planned action."
The Royal Mail said the current wave of strikes had led to a backlog of 35 million items of post but the union said that figure had increased to over 100 million.
The company insisted that some mail was delivered today.
Postal workers wave to passing motorists beeping their horns in support of the strike as they stand on the picket line outside the Bristol Mail Centre on October 29, 2009 in Bristol, England.
Postal workers picketing at St Rollox Mail Centre, react to passing support on October 29, 2009 in Glasgow, Scotland.
