The official result of the ballot is due tomorrow, Wednesday September 15, when union leaders are expected to announce dates the action will take place.
The strike is set to take place on a regional basis, with London being one of the first regions to be affected.
There is still a chance that the walkout can be avoided, as talks are understood to be ongoing between Royal Mail and the Communications Workers Union, after a meeting on Friday.
Both sides have said enough progress has been made to allow them to continue talks in a bid to hammer out a last-minute agreement.
In yesterday's Evening Standard, CWU deputy general secretary David Ward said: "Enough progress has been made for the talks to continue this week."
The CWU decided to issue a strike ballot last month after dismissing Royal Mail's 14.5% pay offer over 18 months, with 10% linked to increased productivity. The CWU branded the offer as having "more strings than the Philharmonic Orchestra" and has said it wants an 8% no-strings, upfront payrise.
Ballot papers were sent out to 160,000 postal workers, the majority of whom are expected to be in favour of strike action.
Royal Mail chairman Allan Leighton has already called the planned strikes "commercial suicide", because the company is struggling to stem losses of 拢750,000 a day.
The postal operator has also been in the news this week amid claims that it exaggerated losses to justify plans to axe 30,000 jobs.
Last week, Ward called for an inquiry into the company's finances, which are to be examined by the Commons Trade and Industry Select Committee, when it looks at how the deregulation of the postal sector will affect Royal Mail's financial position.
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