Halifax Post Office on Commercial Street is shut today due to strike action.
Members of the Communication Workers Union employed in Crown Post Offices are involved in a long-running dispute over jobs, pay and closures.
It is the 12th round of industrial action since Easter.
Crown offices are the larger centres found on high streets and there are plans to close 75.
The union said 4,000 employees in 372 Crown offices are affected.
Post Office bosses claims its plans were essential to stem losses and turn the business around.