Around 900 members of the Shropshire and Mid Wales Branch of the Communication Workers Union were expected to have taken part in today's industrial action.
There were picket lines outside post offices across the county, including Shrewsbury and Telford, as well as in Welshpool in Powys.
The workers are striking over pay and further action is planned for Wednesday next week.
The leader of the Communication Workers Union (CWU) declared Friday's industrial action as "the biggest strike in the UK since 2009", as he said more than 115,000 postal workers were out protesting over pay.
CWU general secretary Dave Ward says his members voted in favour of the strike by 97.6 per cent in a ballot.
Ruth Meadows, secretary of the Shropshire and Mid Wales Branch of the Communication Workers Union, said the union's members were being faced with unprecedented increases in costs and called for Royal Mail bosses to hold talks over a fresh pay deal.
Ms Meadows, who had visited three pickets on Friday morning, said: "It is over our pay negotiations. Obviously Royal Mail have offered us five per cent but what the public don't realise is the five per cent is with a lot of strings. One is a target of what we should achieve which is not achievable and we would not get that five per cent unless we hit the target – so we don't get the five per cent.
"Also, five per cent is not in line with inflation and the extra costs that members are facing."
She added that even if workers received the full five per cent, it "would not scratch the surface" of rising costs.
Ms Meadows said workers wanted Royal Mail to hold further discussions over the situation, adding: "They just feel the business is not listening to its staff."
She added: "What we would like is for them to come to the table to talk, just to talk. You cannot get anywhere if you are not talking to get to some kind of middle ground."
A Royal Mail spokesman criticised the striking workers, saying: "It is putting jobs at risk and making pay rises less affordable. We are losing £1 million a day.
"We must change to fix the situation and protect high quality jobs.
"We want to protect well-paid, permanent jobs long-term and retain our place as the industry leader on pay, terms and conditions. That is in the best interests of Royal Mail and all its employees.
"We apologise to our customers, and the public for the inconvenience the CWU's strike action will cause.
"We have offered to meet the CWU numerous times in recent weeks, but they declined each invitation, preferring to spend their time on the political agenda of the UK trade union movement.
"We remain ready to talk with the CWU to try and avert damaging industrial action and prevent significant inconvenience for customers."