An Post has improved its levels of delivery on last year but still falls short of targets set by Comreg.
The findings were part of Comreg’s first quarter report on the quality of service performance of An Post published today.
According to the report, 98 per cent of all mail was delivered by An Post within three working days, however, this falls short of the 99.5 per cent by the regulator.
The report said that 76 per cent of single-piece priority mail was delivered within one working day throughout the State.
However, it added that service levels continue to vary, with mail posted outside Dublin for delivery in Dublin receiving a poorer quality of service than mail posted and delivered within the capital.
Commissioner of Comreg Mike Byrne said: "The national economy needs an efficient and reliable postal service.
"ComReg remains committed to continuing to actively pursue the issue of quality improvements with An Post," he added.