In the ongoing pay dispute, thousands of postal workers have voted in favor of additional strikes.
According to the Communication Workers Union (CWU), which represents more than 110,000 postal workers at the Royal Mail, more than 95% of employees who cast ballots wanted to go on strike.
A Royal Mail representative expressed "disappointment" with the outcome of the vote.
Workers went on strike over the holiday season, and the recent vote grants the union a six-month strike authorization.
Royal Mail claims to have offered a pay agreement worth up to 9% over 18 months, but the CWU is asking for more given how quickly prices are rising.
The CWU is against any proposed changes to the working environment, including making Sunday work mandatory.
"We remain committed to sitting down with the CWU, resolving this dispute, and agreeing a pay and change deal for our people," a Royal Mail spokesperson said. ".
"We kindly request the CWU to give our best and last pay offer serious consideration and to join us in transforming Royal Mail and securing its future. That is best for Royal Mail and all of its employees, they continued.
