Members of the Communication Workers Union mounted picket lines outside Royal Mail offices across the country, reports dpa news agency.
The Union said more than 100,000 workers are involved, making it the biggest strike of the summer.
The action follows a walkout last week and there will be further stoppages on September 8-9.
The action is in protest at a 2 per cent pay rise, although the company has said more money is on offer.
CWU general secretary Dave Ward said: “There can be no doubt that postal workers are completely united in their determination to secure the dignified, proper pay rise they deserve.
“We can’t keep on living in a country where bosses rake in billions in profit while their employees are forced to use food banks.
“Postal workers won’t meekly accept their living standards being hammered by greedy business leaders who are completely out of touch with modern Britain.
“They are sick of corporate failure getting rewarded again and again.”
CWU deputy general secretary Terry Pullinger said: “Our members worked miracles during the pandemic and know full well what they are worth.
“They are fighting for a no-strings, real-terms pay rise – something they are fully entitled to.
“Those managing Royal Mail Group are treating our members with contempt by imposing such a minimal amount.”
A Royal Mail spokesman said: “The CWU’s self-centred actions with the wider trade union movement is putting jobs at risk, and making pay rises less affordable.”
–IANS
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